So Apple is unifying their version numbering across the board to roughly correspond to the coming year number (like Windows 95 or car model years for example.) I don't recall seeing this explicitly mentioned for Fairplay anywhere, but I think Version 26 has essentially replaced Version 5, with some new extra changes sneaked in. Hard to guess if version 26 certificates will work with what up to this point had been version 5, but I hope so? https://www.cnet.com/tech/services-and-software/apple-confirms-switch-to-ios-26-naming-convention-heres-why-that-matters/