No-CD & No-DVD Patch troubleshooting: The most common problem getting a No-CD/No-DVD patch to work is ensuring that the No-CD/No-DVD patch matches you're game version, because the games exe is changed when a patch update is applied previous versions won't work.
This is likely the end of the line for the MLB 2K series since Take-Two's agreement with MLBPA expires this year. Post-release support for MLB 2K12 has been pretty awful, with the PC version left completely untouched and consoles last seeing a patch in June. This year's title isn't terrible, but the game isn't without its bugs and shortcomings.
Mlb2k12 Pc V 1.2 Patch