My 2020 W-2 PDF won't upload to TurboTax it keeps saying upload failed and i don't know why

Then just enter the W-2 manually.

If you have it in hand then key it in instead of wasting a morning fighting with the technology.  It takes about a minute or two to key it in.

Either your employer is not an import partner  OR  they have not made access available yet ... if you have a paper copy in your possession then manual entry is an option.