After entering the NBA 2K20, the in-game update screen pops up but it stuck at 0%.
How to Fix the "downloading game updates" Bug
Disable the Windows firewall and antivirus program. Restart your modem. Then check the game. If still the same issue, try the second solution.
Go to C:\Program Files (x86)\Steam\userdata\*steam user id*\841370\local and delete sync.bin. Then launch the NBA 2K20. If it is still stuck, try the final solution.
Uninstall the NBA 2K20. You can easily delete the game by right-clicking the NBA 2K20 in the Steam library. Then exit Steam and reinstall the Steam. After that install the Steam. Finally, just download the NBA 2K20.
You should also check your disks. You should leave enough free space on your local disks.
If you want to fix this problem on PlayStation 4, you have to delete the game's saved data.
Please make a backup of your game data before removing it.
Go to PlayStation 4 Settings > Application Saved Data Management > Saved Data in Online Storage > Delete > NBA 2K20
You can able to play the game after deleting the saved data. After deleting the saved game data, I do not know if it is possible to play NBA 2K20 again with your old save, sorry.