I have the latest standalone version of DCS. I originally had the Steam version but I transitioned to standalone recently.
I own the following modules: FC3, A-10C, F-86F, AJS-37, and F-5E. In my DCS profile, I see that I have 5 licenses, for those exact modules. I don't own and have never owned the P-51D Mustang.
Every time I launch I get the same message: "P-51D Mustang" is not authorized to be used with your account. Please, provide a valid serial number.
If I click skip, it tells me "Authorization is valid for 2d 23h 53m. The following DLCs are not authorized and will be disabled", but it tells me the same thing every time I launch. Also, if I provide my FC3 serial number thinking maybe that's what it's from (from Steam where I originally bought it) it accepts the serial number with no error, but the next time I launch DCS it asks for a serial number again.
I have run DCS clean and repair commands. I'm not sure what else to try. Thanks!