I am asking after reading other previous posts in this topic that appeared to be happening on Apple/ ioS devices. I do not use Channels on any Apple devices. Two Fire TV's.
Perhaps some additional details/context would be helpful. As is, the message seems to be saying that your tuner provides only 2 streams, and both were currently being used when you requested an additional stream.
Yes, it is a HDHomerun Flex Duo (2 tuners).
Then the message means exactly as it states: both tuners are currently in use while you are attempting to access an additional stream.
I would hazard a guess that you are trying to change channels on one device while the other is currently watching something or you are recording something. What is likely happening is that the feed you are switching from has not been fully released before trying to tune to the new channel.
I would suggest that the next time this occurs that you go into settings on the client device you received the error message on, and submit diagnostics, followed by an email to [email protected] . They would be able to better determine the root issue of your problem.