Many arcade systems, such as the SNK Neo Geo, Capcom Play System (CPS), and PolyGame Master (PGM), require system hardware BIOS files to boot. If files like neogeo.zip or pgm.zip are missing from your ROMs directory, or if they are outdated, the games dependent on them will fail the validation check. How to Fix the "Unknown" Romset Error Step 1: Identify Your FBNeo Version
What are you running FBNeo on? (e.g., PC, RetroArch on Steam Deck, Raspberry Pi/RetroPie) fbneo romset unknown
Load this DAT into ROMVault or ClrMAMEPro, point it to your ROM folder, and rebuild. When your ROM collection matches the DAT 100%, you will never see an "unknown" error again. Many arcade systems, such as the SNK Neo
This article will explain, in detail, why the "fbneo romset unknown" error occurs and, more importantly, how to fix it permanently. You are using an older or newer ROM
You are using an older or newer ROM set than the specific version of the FBNeo core you have installed.