If you have verified all the above and still get Error 4, it is highly likely your game files (ROM/Dump) are corrupted or incomplete. Error 4 essentially means "I found the game EXE, but I cannot attach the necessary brain (DLL) to make it run." If the brain is there and valid, the dump is likely the issue.
Teknoparrot 1269 - nothing is working · Issue #238 - GitHub teknoparrot failed to load dll error 4 exclusive
If the above fails, configuration corruption is the culprit. If you have verified all the above and