We support up to 3 device sessions for each customer account. If you receive the message: 

"The device limit for your account has been reached. Please sign out of a device to watch"

Then please sign out of one of your devices to add your new one. Each browser counts as 1 device, so often signing out and clearing the cache / cookies from your browser will resolve this issue. 

e.g. if you are signed into the app on your phone, through chrome on your laptop, and through safari on your phone, you are signed into 3 devices.