Before adding a camera to your current blockchain identity (Ucam account), make sure it is not connected to any other one. It could happen when you logout the account or switch account.
You can check if your camera is connected to the former blockchain identity here. If so, make sure to de-register and reset the camera first. Then try to add it again to your new blockchain identity (Ucam account).
If you keep experiencing connection failure, please contact us at firstname.lastname@example.org.