Build Number: 5.0.12973.0
I have completed “1514, Lithuania” in the The Rise Of Moscow and unlocked the corresponding unlockable content, but the next level “1552, Kazan”, is not playable. This can be seen in the screenshot below. Restarting the game, restarting the PC, and “verify integrity of game files” did not fix this.
Update 1: After starting up the game a few hours later, now all of the levels besides “1066, Hastings” are locked… I would add a screenshot but as a new user I can only embed one media item.
Update 2: I have solved this by creating more space on my drive then deleting everything in Documents/My Games/Age of Empires IV/Users/[ID number]. I believe it was a corrupted file due to full drive.