You can reinstall the default GoZ like this:
1.Rename the Pixologic folder at C:\Users\Public\ to PixologicBAK. This keeps a copy of your GoZ installation in case you need to restore anything.
2.In the C:\Program Files\Pixologic\ZBrush 2021\Troubleshoot Help folder, run the GoZ_for_ZBrush_Installer_WIN.exe file. This will rebuild your GoZ installation.
3. Start ZBrush and press Preferences>GoZ>Force reinstall. Make sure you choose the correct path for the application you want and make sure you select “Install”.
4. If the application is not found then use the Preferences>GoZ>path to button to select the path. Make sure to select “Install” when the option appears.