This confirms your ROM is corrupted or from a wrong source. You cannot fix this manually unless you find a binary patcher (rare). The only solution is to grab a version.
Follow FBNeo development on GitHub to be aware of significant changes that might affect your ROM set. The project is active, with regular updates that refine emulation and add support for new games. romset is unknown fbneo fixed
The "fix" for this error is rarely found in modifying the emulator itself, but rather in rectifying the ROM set. The most robust solution is the use of DAT files. A DAT file is a blueprint that lists the exact file names, sizes, and checksums required for a specific emulator version. By using a ROM management tool (such as ClrMAMEPro or RomCenter), users can audit their collections against the specific DAT file for the version of FBNeo they are running. These tools identify which files are missing, misnamed, or incorrect, allowing the user to rebuild their archive to match the emulator’s strict specifications. This confirms your ROM is corrupted or from a wrong source
FBNeo primarily supports 2D arcade games. Attempting to run 3D arcade games (like those requiring MAME) may trigger this error. Follow FBNeo development on GitHub to be aware
If you try to load a clone ROM (e.g., Pac-Man [USA] ) but do not have the parent ROM (e.g., Puck Man [Japan] ), FBNeo will not know how to read the shared files and will give you an error. How to organize your files: