Premiere Pro 2022 - No Export possible

I have been trying to create and export a video for 5 days now. After each edit or addition of new sources, I had to save, close and restart the programme. That was annoying.

Now the video is ready for export, but neither H.264 nor MPEG4 nor AVI render out. It keeps getting stuck at 3-6% and nothing happens. Not even via the Media Encoder. Regardless of the output quality.
I have already tried the previous versions (22.0.1 and 22.0). It didn't work here either.
With version 18.4.3, the project file can no longer be opened.

I need a solution!