The uplay_r1_loader64.dll error typically occurs when the game fails to load the required uplay_r1_loader64.dll file, which is a part of Ubisoft's Uplay platform. This file is essential for the game to function properly. When the file is missing, corrupted, or not registered correctly, the game crashes, and the error message appears.
He found the solution wasn't just reinstalling the game, but ensuring the correct version of the launcher was communicating with the game. The uplay_r1_loader64