I have tried the following ROM sets .151, .149 and a .155 set I found online.
I used ROMcenter to audit the games and try to fix those that appear yellow or red.
I used MAMEPLUS! latest version initially to open and check the ROMS, most that ROMCenter stated were working actually did but there were exceptions.
I used Maximus Arcade to create a favorites list of just the working ROMS I wanted, pared it down to about 200. I was ready to go, and all worked!
Then, Maximus Arcade was opened about a week later and almost all of the ROMS were not found. I checked the path to ROMS, nothing had changed. I tried opening them in MAMEPlus! directly, and they still were not found. I checked the path to ROMS in MAMEPlus! and it was correct. I then removed the ROMS and readded them, had MAMEPLUS! rescan. Still can't find the ROMS.
So:
I tried MAMEUI .149 - no nag -highscore init. I moved the .149 ROM set in, pointed to the correct directory, it build the game list. I again checked them with ROMcenter, and opened games that were listed as working with MAMEUI and voila! The games were working. Unfortunately, Maximus Arcade has a bug and won't work with MAMEUI .149. So I tried other frontends to see if I could find one I liked. Hyperspin seemed to be downloading malware, or just wouldn't open (I downloaded from their website too). GameEX worked, but wasn't a fan of the MCE style. mGalaxy was ok but tough to pare out the junk ROMS. Regardless, I went to open ROMS in MAMEUI after about 2-3 days of working on frontends and voila again...now the ROMS can't be found. I again checked the directory in MAMEUI, removed and readded/rescanned the ROMS. Still won't find them. Just like before it's not all the ROMS but most of them.
So:
I read up more on maximus arcade issues and bugs. I ensured the right directory to the ROMS, I changed the ROM path from 'short' to 'long'. I deleted the game file and had forced a rescan. It still can't find almost all of the ROMs when I try to open them, but no surprise they aren't found when I try to launch in MAMEPlus! too. I keep the ROMs in the emulators main folder, in a ROM folder without any subfolders, I have not unzipped them. I tried changing the ROM version from .149 to .151 or vice versa wtih both emulators. I'm formally now stuck...
I can provide more details if it is helpful. My cabinet is built and waiting!!