If you're in a hurry, here's a fast recap of the most likely fixes:
A frequent complaint among Steam players is being asked for an activation key that Steam never provides. unable to locate uplay pc watch dogs 2
Use the "Move Installation" feature within Steam or Ubisoft Connect rather than dragging and dropping folders in Windows Explorer. If you're in a hurry, here's a fast
Many players found success by updating or replacing the specific DLL files in the Ubisoft Connect directory. If you're in a hurry