@PapaBearUk Good day.
Each tapo camera supports up to 2 simultaneous video streaming, so uses could use up to 2 devices to live view the camera at the same time using the Tapo APP or the RTSP.
For playback, uses could view the Playback on only 1 device using the Tapo APP at the same time.
If you are using a 3rd phone to Live view / use 2nd phone to watch Playback it will prompt ’ reached your device limit' message
If you have shared your device to other account before, it is recommended to stop sharing the device temporarily and test if the message pops up again when you are suing <=2 phones.