If you have an aup3 file you can’t open you can try the recover procedure here: Corrupt or Otherwise Broken Audacity Project Recovery
You may have problems getting Audacity to open if you have anything in the Windows: C:\Users<your username>\AppData\Local\Audacity\SessionData directory. If you have an unsaved-aup3 file, you can try renaming it to .aup3 then try the aforementioned procedure.