Problems with Ubisoft's own Uplay servers have dogged the launch day of Watch Dogs yesterday, which has meant some PC users can't even authenticate their Watch Dogs purchase and therefore play the game. Similar Uplay issues are effecting the mobile Companion App - we've had multiple connection errors since downloading the App yesterday.
While the company acknowledged the strain to their servers, the problem is still persisting: Ubisoft have flagged that they've been working on the issue since yesterday and are seeing some improvements.