If you have tried all of the above and still see , it is time to reach out to official channels.
The error message in OMORI typically appears when the game cannot verify your Steam ownership or connect to Steam's client. Here’s how to fix it: Steam Has Not Been Detected Omori
This step is technically a grey area. It involves replacing the DRM file with a modified version. However, if you legally own the game and just want it to work without launching Steam (e.g., for offline play or to bypass persistent errors), this is a solution. If you have tried all of the above