When you try to run the game Piere Solar.bin and Piere Solar.iso (in the same folder for audio tracks. though I do not use) displays a message. Core Genesis Plus GX, Picodrive. Previously, this game worked on 1.3.6.
Go into settings > core and set 'Check for missing firmware before loading" to OFF.
In newer RetroArch versions, emulator cores can be programmed to make sure that the firmware associated with a console is in place before the emulator core starts.
Even though this particular game may have had adequate firmware to run in the past, it sounds a lot like those emulators are missing one or more firmware files that have been coded as mandatory for proper emulation.
What firmware, if any, do you have in your system folder for those emulator cores? Do the filenames and md5 checksums match exactly what is listed here: https://github.com/libretro/libretro-super/blob/master/dist/info/picodrive_libretro.info#L13-L23 ?
Or, as hunterk said, just turn the feature off! 
I can’t reproduce any message here, either the option in Settings --> Core set ON or OFF. Update retroarch I guess
Thanks! Names of bios This important information is nowhere seen. But I just unzipped BIOS_pack.zip in the folder / system.
Are you saying that adding the BIOS files ended the error message and returned your ROMs to their expected function?
Yes, simply by copying all the files were not copied. when I went from 1.3.6 to 1.4.0.
Great, I’m glad a BIOS set did the trick!
nevermind i figuered out that i had to switch to advanced settings what an odd feature
nevermind that I found the settings section but I still cant find the core section inside of the settings section.
you say go into settings but I can’t find the settings section…? Im using Retroarch