Please insert game disc error

[GenericName]

I recently just bought my first Dreamcast and it came with a bunch of demo disc and a copy of Sonic Adventure. Whenever I insert Sonic Adventure it says “Please wait while disc is being checked” and soon after when I try to play the message “Please insert game disc” pops up. However when I try to play the demo discs they work perfectly fine with no issue whatsoever. I assumed it was a problem with the Sonic Adventure disc so I cleaned it and resurfaced it but even after the same message still comes up. I’m really at a lost at what the problem might be and if someone might be able to help me that would be amazing.