Audacity 2.4.2 wont convert aup to wav to Windows Media Player

exported to wav, but comes up on playlist as aup, wont burn.
some errors I get are “file is missing media useage rights” or burn rights, WMP cannot play the file, the player may not support the file type or codec that was used to compress the file.
It worked last week with no problem. Windows 10

I think rather than blindly mess with this, it would be good to reveal filename extensions to see what Windows thinks you did.

What you think you did and what Windows thinks is different. It’s possible you have an AUP file and a WAV file with the same name and the only difference is the extension which Windows helpfully hides from you. Time for the reveal.