What am I doing wrong?

You're screen shots tell a story of you trying (maybe not on purpose) but trying to confuse your poor computer. The configuration will not change on its own, you are changing it. You are opening a second instance of the MOXF Editor VST - which you can do, if you have used the FREEZE function properly. If you have not engaged the FREEZE function then you have opened two instances of MOXF Editor VST while you only have one MOXF hardware. This can be a problem.

Our guess (and we can only guess based on the info/clues you have given):
Since you have a UR22 - and are at some point using it as your AUDIO INTERFACE, then at some point, probably because you don't know how to setup the MOXF VST yourself, you launched one of the MOXF Extensions project TEMPLATES (which setup the MOXF as your AUDIO INTERFACE instead - did you know that?) Well that is what we think happened. You unknowingly, and multiple times, have used a TEMPLATE that has confused your computer as to your workflow

My suggestion: DO NOT, repeat, DO NOT use any of the provided MOXF Templates; especially if you are not certain they setup for EXACTLY what you want to do. I can tell by your ports that you are using some pre-configured setup, that obviously has nothing to do with how you actually want to work. To us it is unclear as to how you actually want to work.

If you have an idea about which device you want to act as your audio interface - and when, let us know and we'll help you straighten this all out.

Makes sense.
When I unplugged UR22, moxf must have taken in the computer audio device (?)
Now, BEFORE switching the moxf on (always connected to my computer through usb) I get the screenshot "sound before".
AFTER switching the moxf on I get the screenshot "sound after".
Can't recall if the "line 2 moxf" device was there before, or if it has something to do with the ports problem.

You still haven't told us how you want to setup to work. Either of these devices UR22 and the MOXF can act as your audio interface. We'll make it easier, which one is connected to your speakers?

UR22 acts as the computer sound controller/drive. It is always plugged in to it through usb.
At the cubase I use it to record voice though microphone, thus enabling it at my needs.
I do not need it to be active at (or antagonistic to) Cubase right now.
I only want to work with moxf through usb (vst).
I also attach you a screenshot of the device setup window, where it can be seen that audio inputs are "not connected" (this after the aforementioned manual synchronization).

I only want to work with moxf through usb (vst).
I also attach you a screenshot of the device setup window, where it can be seen that audio inputs are "not connected" (this after the aforementioned manual synchronization).

In order for the MOXF to act as your audio interface you will need to connect the Main Left/Right Outputs of the MOXF to your speakers. Just want to be clear.. The Speakers must always be connected to the device that is acting as the audio interface.

If you are using the UR22 as your audio interface, expect signal to ultimately be routed through it before going to the speakers.
If you are using the MOXF as the audio interface, then naturally you will need to connect its audio outputs to your sound system (or you can monitor in headphones connected to the MOXF).

You at some point, switched between the UR22 and the MOXF (both of which happen to use the same driver, each with its own protocol), but the computer did not register this as you switching back to the MOXF or it could be remembering a previous preference. When it toggles to ("2-MOXF...") it is thinking you now have a second keyboard - it is not a big issue, but it is something that has been cached in your preferences, it will still communicate with the device.

This is really a Cubase management thing - you can have several different PRESETs stored so that when you want to switch between UR22 (say to record vocals) and then back to the MOXF, you will not have to scratch your head, except for the first time you set it up. From then on you only need to switch the connection going to the speakers to the device acting as Audio Interface.

(If the numbering bothers you, contact Steinberg through your MySteinberg Account, there is probably a simple method to clear the preferences).
Cubase is designed to be able to swap audio interfaces without having to shut down the program, so once you get the connections you need locked in, this will not be a major issue, at all.

You do not have disconnect the UR22 from the computer. You do need to move the speaker leads from the UR22 to the MOXF, **** Or there is another option... you can use the UR22 as the audio interface for your MOXF.

In this setup, the main L/R outputs of the MOXF connect to the inputs of the UR22. The UR22 stays connected to the speakers.
in the EDITOR VST, you would select the two Ports of the UR22 as the AUDIO RETURNs to Cubase. In this scenario you only have once STEREO connection to the computer, so USB 1/2 nor USB 3/4 are used from the MOXF... the audio for your MOXF travels analog to the UR22, is then converted to a stereo USB signal that the UR22 sends to the computer (digitally) and to your monitors (analog)...

I started Cubase in Safe Mode, Disabling (momentarily) the preferences but I still got the "port open error".
Suggestions most appreciated!

Safe mode will not work. I did suggest you contact Steinberg through your MySteinberg Account (email) for the preferences trick (Safe mode has nothing whatever to do with your Cubase preferences so that will not work at all). Even if you trash your old Cubase preferences this will only improve the number of instances number, it should not and will not fix your "Port Open Error" - which is a totally separate matter (totally).

This PORT OPEN ERROR has to do with your basic settings. We can review those again:

If you are going to use the MOXF as your interface... here's a checklist:

1) Make sure your speakers are connected to the audio L/R outputs of the MOXF and that the MOXF is ON when you launch Cubase.
2) When you launch an EMPTY PROJECT in Cubase: Check MIDI setups: go to DEVICES > DEVICE SETUP > MIDI > MIDI PORT SETUP > make sure only PORT 1 for MOXF is marked in the "IN ALL MIDI INPUTS" column, clear the mark for all others in this column.
Check your Audio Setup: Go to VST AUDIO SYSTEM > Yamaha Steinberg USB as your ASIO Driver.
3) Go do DEVICES > VST INSTRUMENTS > under EXTERNAL select "MOXF VST"
4) When asked to create a MIDI Track create it. This track will be assigned to the MOXF VST; the Editor will launch

In the MOXF EDITOR VST go to FILE > SETUP > activate the DETAILS on the USB setting so you can see your options. Anything with an exclamation point is bad news. Find the Ports, if you cannot stop. Nothing you do beyond this will help. If you do find the ports continue - by selecting Port 1 where appropriate for IN and OUT and Port 4 where appropriate for IN and OUT.

In the MOXF EDITOR VST go to FILE > VSTi SETUP > make sure the USB 3/4 (MOXF internal tone engine) and USB 1/2 (A/D input and specifically assigned Parts) are assigned.

You were right about the Cubase preferences stuff.
It seems there was another way round: When I switched usb's I reconnected it at another slot. It seems windows remembered the specific slot and thought I connected another machine when I used a different slot! Stupid but real.
Thank you for your guidance.

No worries!

I have the same problem. EDITOR doesn´t SYNC with the MOXF. All checklist is "checked" but still got message of port open error when start editor as VST instrument in Cubase10.5 on my MAC PRO Catalina OS.
On the EDITOR PORT SETTING view I have the same "Ports in the host app .... not properly set"
But that continuous to be there when I set it like in manual.

On standalone ...the editor syncs when I set port1 as midi out...but also as midi in (not avaible as VST on Cubase), and port 4 as in and out.
No problems here!!! ¿?

I also started with the template of 16 midi tracks and one audio track for ADinput...´cause thats what I want....to be able to have my MOXF on CUBASE to build a song using the adventage of both system (HW&SW). Like Dionyses

Please, tell me if u need some data ...to provide.
Thanks in advance