I have the same issue on a PC. It is a 22 Core top of the line system with striped SSD's and when I do a quick export or even try to render in the editor it does't work. This is a Windows 10 system with latest MS updates and Graphics drivers. I knew I shouldn't have gone back to Adobe since I am not a MAC user. $$$ down the drain.
This does not sound ideal. I understand that when you try to render or export the project using PRE 2020, it does not perform any action. I appreciate the fact that you have kept your OS and GPU drivers updated. Could you share more information?
What are your system details(RAM, GPU, Processor, etc)?
Does it happen to every project?
Was it ever working fine before with the same version?
I have a suggestion. Please try running the application as administrator and then check if it works.
Looking forward to your response.
Note: I have moved this message to a different discussion so that we can help you better.