Photoshop 2020 has a known issue with Egnyte Desktop App for Mac. When a user tries to open an existing file and then makes a change and saves, it gives an error saying the file already exists. This is an error with Photoshop, not Egnyte Desktop App for Mac. When the Save in Background feature on Photoshop is turned off, files are saved with no error. This is a known issue, and Adobe is aware.
The workaround is to disable "Save in Background" and "Automatic Save Recovery" from Preferences.
This issue will be resolved in Mac Desktop App 3.6.0.