Here are steps you can follow to potentially fix the uplay_r1_loader64.dll error in Assassin's Creed Unity:
If the DLL is present but Windows has lost its internal registration, you can manually re-register it using the Command Prompt. Here are steps you can follow to potentially
Open (or your specific antivirus software). Go to Virus & threat protection > Protection history . Locate the entry for uplay_r1_loader64.dll . Click Actions and select Restore . Here are steps you can follow to potentially