Most uplay_r1_loader64.dll errors happen because or other antivirus programs (like Malwarebytes) have quarantined the file.
Go to Virus & threat protection → Manage settings → Exclusions → Add or remove exclusions → Add the game folder.
Steam may also launch Ubisoft Connect to complete the verification.
Don’t worry. This is a common issue, especially with newer Windows updates or after reinstalling the game. The good news?
To prevent it from happening again, add the Assassin’s Creed Unity installation folder to your antivirus list. 2. Manual Replacement from Game Folders