Sound of VST instruments suddenly disappears

So I am using Cubase LE AI Elements 6 which I got when I bought Zoom H6.

Basically I set up everything, recorded some keyboards (VST track, used my own keybard). Then I wanted to record vocals and everything worked well. Suddenly the program crashed and there is no sound from VST instruments whatsoever. And the click is also not there. The settings are the same, the software, drivers etc. updates are up to date. I installed the ASIO driver one more time just in case, nothing changed. I also have no other windows open either, not even a browser. I can hear music etc. on other sites, programs as I also have checked and also through Zoom.

I also got some strange error messages about the VST presets not being able to load. I clicked on “do not ask again” and then closed the window and the instruments seemed to work. Meanwhile, I can record an audio track - that works just fine!

Has anyone seen something like this? I googled with little results. I am on the brink of ditching the whole thing.