Hi,
We're sorry about the trouble with Photoshop 2021 due to the program error. Would you mind telling us which operating system are you working on?
Our product team is working on a fix for the program error. Meanwhile, you can try the steps suggested here: https://adobe.ly/2JZDqZB
If the issue persists, please roll back to the previous version of Photoshop using the steps suggested here: https://adobe.ly/2wH0JjE
Please uninstall the latest version of Photoshop first & select the option to Keep Preferences prior to installing the previous version.
Regards,
Nikunj