Whenever you post to the forums now it would be very useful to those replying to you to have your complete system specs in your signature so that those replying to your question have a better idea of what could be going on.
Having said that the minimum specs you gave in any earlier question gives me this data.
Processor: AMD FX(tm)-6300 Six-Core Processor
3.50 GHz
RAM: 16 GB
Assuming you are using the same system you ran Movie Edit Pro, Version 14.0.0.130 (UDPP3) on it is highly possible that you have no suitable GPU on your system to run MEP 2021 Version 20.0.1.73. and that you need to turn off any hardware acceleration settings within MEPs' program settings and use the 'Compatibility settings (videoForWindows)' setting in the playback section.