HELP - Legends Ultimate CoinOpsX and AddOnX Errors

Hello. I received the Legends Ultimate in December 2024 and purchased a CoinOpsX thumb drive to go with it. It has been working fine up until last week. Suddenly, I am getting the following errors:

"Error reading the AddOnX files. Please run the AddOnX tool again."

"No CoinOPSX file found. Please check the USB drive and try again."

I have tried factory resets of the machine multiple times. I have also tried using both USB slots on the machine in case one slot was bad. I have also ensured that the firmware on the machine has not auto-updated. 

Can anyone give me some clear guidance on how I can fix this? I don't know how to "run the AddOnX tool again" as I don't think I ever ran it to begin with.

Please know that I am not a gamer and I would consider my technology skills adequate. I'm just a guy in his 50s enjoying the nostalgia of his youth with the 7000+ games available.