Hi Odell,

We will try to help you get things sorted As you have discovered the issue was not really the Steinberg UR24C, as getting a different audio interface did nothing to correct the situation. (It was likely not the cause of the issue in the first place). Sounds like a setup issue - and the result of trying so many different things you have confused the situation.

I'm trying to get midi input into Nuendo.

There are several methods to do this. You can use standard 5-pin MIDI cables to connect the MODX to your audio interface. The MIDI OUT of the MODX to the MIDI IN of the audio interface, and MIDI OUT of the audio interface to MIDI IN of the MODX.
Next in your MODX go to [UTILITY] > "Settings" > "MIDI I/O" > Make sure "MIDI In/Out" is set to MIDI (green)

With this setup - Nuendo will be addressing the MODX as the MIDI Ports found on your Audio Interface - in other words, expect to use the name of the audio interface as the MIDI Ports when routing signal within Nuendo.

Alternate Method:
Connect the MODX to an available USB Port and use the "Yamaha Steinberg USB Driver". The USB connection will allow for MIDI communication, this is true whether or not you are using the Audio capability. That means you can use the USB-MIDI connection without having to use the MODX's audio interface portion of the USB connection.
When using the MODX via USB for MIDI - you must set the "MIDI Input/Output" to USB (green).

I have the MODX 7 going into a Focusrite 4I4.

As stated MIDI OUT of the MODX to the MIDI IN of the audio interface, and MIDI OUT of the audio interface to MIDI IN of the MODX. Set the MODX to MIDI I/O = MIDI

This takes care of the MIDI signal (you cannot hear MIDI signal) so you additionally need to route the Main L/R outputs of the MODX to the device acting as your AUDIO INTERFACE... it will be responsible for sending the signal on to your speaker system. The Audio Interface is the device that connects directly to your speaker system.

I've tried vst instrument input nothing.

? ? ? Not sure what you mean here ???

I've tried line input through the focusrite control and still nothing.

To connect AUDIO from the MODX to your computer you would connect a pair of 1/4" signal cables from the MAIN L/R Outputs of the MODX to two adjacent inputs on your audio interface (treat them as a stereo pair). This has nothing to do with MIDI - (your goal was to get MIDI into Nuendo). You must have your MODX connected to the device that is acting as your audio interface - of course, the audio interface is what is connected to your speakers.

MIDI is not sound - you send MIDI to Nuendo - it is captured and echoed back to the MODX via MIDI Tracks. Now the MODX tone generator makes sound... that sound is the AUDIO that you want to record and hear... That signal must be routed to your AUDIO INTERFACE - will allow you to send digital AUDIO into Nuendo... and analog AUDIO to your SPEAKERS.

Alternate Method:
Connect the MODX to an available USB Port on your computer and use the Yamaha Steinberg USB Driver. The USB connection will allow for Audio communication to and from the computer. That means you can use the USB connection for AUDIO -- the MODX as audio interface. 10 Audio bus outputs are available via USB.

Once properly setup - either interface will be rock steady and should deliver stellar results. Let us know