"playback failed" while playback works?

[Bestboy]

Hi, I installed the Plus addon, which seems to work (no authorization error).
As soon as I start a stream it will load the stream , and the video will start but then the popup says "Playback failed", even while the video is working fine behind that popup window. When I press OK to close the window, the stream stops and i am back to channel selection.
any idea what to do ?
Thanks !