If anyone else has this problem, I'd suggest checking whether you've downloaded the latest version of the DLC and the base game! You only get that message if one (or both) of them is outdated.
I got the same thing on my screen, and I'm sure I downloaded the latest version of the DLC and the Base game ver 5.5.2 (although on the in game screen it says version 5.5.1?)
If this still happens even after you've fully restarted your PC, I'd suggest deleting all your previous 14DWY files and re-downloading everything again.
