If you see #0000000D error code, get rid of a process that interfere with EAC (its name in square brackets). For any other error codes, fixes are universal:
Check your task manager and get rid of any software that you think can interfere with EAC (RGB, tray minimizers, tweaks, etc).
If you use third-party antivirus - make sure to add EAC to exclusions.
Proceed with driver signature verification by pressing "Start".
After it's finished, you'll be prompted either with the list of unsigned drivers or message that everything's fine. In first case, depending on what drivers are unsigned, you may need to reinstall/update your GPU drivers or run sfc/dism.