MIDI not producing sound

After my Cubase 10.5 locked up from some corrupted VST3s I had to use task manager to close the program. That happened repeatedly and Cubase stopped using the MIDI signal to produce sound. The midi shows up on the indicator in the lower right and in assigned channels but it will not trigger the Vsts.

Make sure MIDI through is active, and no filters are set.

I double checked those. I disabled my preferences and reinstated the factory defaults, etc. I even re-installed Cubase.

Someone please help me. I am not a novice at this. I’ve been using Cubase since the early SX series and I’m baffled. I still have Cubase 6.0.5 installed because I have one 32 plugin that I still need the midi files from, Groove Agent 2. I also have Cubase 9.5, 10.5 and now 11. When I had the above mentioned crashes I stopped being able to see or hear my 64bit (the only ones that work on those versions) plugins. I could see in the lower right “midi in” indicator that the program was receiving the midi data. Both keyboards initiate the Retrospective Recording. When I try stand alone mode in any of my plugins they work fine. After I uninstalled all of the Cubases and reinstalled them in order I did manage to get Cubase 9.5 to operate normally. Cubase 10.5 still does not work so I bought Cubase 11, thinking that a fresh install might solve it. Now I can record the midi input but still cannot hear it while playing, thus making recording tracks very difficult. I have run the repair on the uninstall menu in W10 using the individual .msi files to no avail. I thought that any files that were corrupted by the initial crashes in 10.5 would be fixed by that. Is there a real expert in here who knows what system file connects the midi in to the individual channels in Cubase that might be corrupt and causing my problem. I’ve been under a deadline and this is not helping. I’ve even used my Steinberg, NI and Arturia plugins in Acid 10 with the same keyboard settings and they all work. Any experts on here?

So do the VSTI receive the MIDI data (visible on the rx lighting up on teh GUI)?
Input monitor is activated?
What VSTi are we actually talking about?
If you have MIDI on the transport in and on the MIDI channel, but not in the VSTi, and you can record the MIDI data, but can not hear the VSTi then it is a MIDI thru setting not being correct. Where did you set MIDI thru?

I have exactly the same problem! I’m using Cubase Pro 10.5 on W7 (updated from 9.5). I also have Arturia plugins, but surely that can’t be it. Also have HAL Sonic 3 , Grand 3, Groove Agent 5. Can record Midi on a track, but cannot hear any VSTi in playback from external midi keyboard. Any ideas?
I’ve spent weeks on this to no avail !