After receiving a few similar reports, we've been researching this issue and have found that it was caused by the newest update to the NVIDIA 550 drivers. As this package was published in the Ubuntu repositories, we have gotten in touch with the Ubuntu team to try and resolve it from upstream.
In the meantime, you can apply one of the following two workarounds to resolve this issue on your system:
Workaround 1
Downgrade to the previous NVIDIA 535 drivers using the Additional Drivers utility: Activate NVIDIA Graphics Card - Zorin Help
Alternatively, you should be able to open the Terminal (Ctrl+Alt+T) and enter these 2 commands:
sudo apt remove nvidia* libnvidia*
sudo apt install --install-recommends nvidia-driver-535
Afterwards, restart your computer to apply the changes.
Workaround 2
Switch to the Xorg display server by following these steps:
- Restart your computer
- At the login screen, please select your username.
- Click on the gear icon in the bottom-right corner of the screen to open the desktop environment menu.
- Select the "Zorin Desktop on Xorg" option, not "Zorin Desktop" or "Zorin Desktop on Wayland".
- Afterward, log in normally again.