You didn't say which configuration you were using when you were pressing a piano key and not getting a signal. And which keyboard you were pressing (on GUI, or Montage). Since you show two configurations in your picture - I'm not certain which you were using and exactly what you tried doing.

The tutorials cover using Montage as the audio interface - so it may be best to stick with that configuration until you get something working. Then feel free to branch out to use different audio interfaces if you choose (configuration #2 in your picture).

Using configuration #2 - make sure that the [A/D INPUT ON/OFF] button is pressed and illuminated. Make sure the gain control on A/D input (the "GAIN" knob directly under the A/D input on/off button) is set properly (not all the way off). Set by having the attached JV2080 output sound and look for the PEAK light to illuminate. Set so you are just under having the peak LED illuminate when the JV2080 is at its loudest for what you're going to record.

If you use configuration #2, your MIDI configuration will be set to USB and not 5-pin DIN. Therefore, when you press Montage piano keys - the MIDI data does not go to your JV2080, but goes to your computer. Your computer has to send the MIDI back to the JV2080 to complete the loop IF you want your Montage piano keys to make the JV2080 sound. I'm not sure if there is a configuration for this in Samplerobot so you can audition devices not directly MIDI-tied to your audio interface's MIDI port. Maybe there is - but it's not necessarily needed. You should be able to use the on-screen keyboard in the samplerobot interface to press keys and play sounds on the JV2080.

In order for this to work, you have to have your MIDI output in Samplerobot configured for MONTAGE-3 (Montage Port 3). This will make sure the MIDI makes its way to the 5-pin DIN port. If you have the MIDI configuration as MONTAGE-1 (Port 1), SampleRobot will play the keys of your Montage and not the JV2080. Playing the keys of the Montage will have Montage producing the sound from its own tone generator.

Also, on your A/D configuration on Montage - you may want to check to see that the audio output for A/D is set to Main L&R. This will send the output of the JV2080, through the A/D input, to the simplest-to-deal-with digital channel Main L&R.

Thank you, Jason.

I'm sorry I did not say it correctly and caused a misunderstanding. In fact, I've used both configurations. The way you said was right.

I recently contacted the Samplerobot Support team, and I figured out why I could not record. they said it was a conflict with Apple's Mojave OS.
Foolishly, The answer is what i've linked before. ( https://twitter.com/SampleRobot/status/1116287601932165120)

Once again, thank you for the friendly explanation.

Glad you got that sorted and informed us of the resolution. Others with issues on Mojave can benefit.