Tuner In Use?

I have an HDHomeRun Duo and 2 Apple TV’s (newest model). Why do I get the message “Tuner In Use” if I try to watch Channels DVR local channels on one Apple TV when the Channels DVR local channels are playing on the other Apple TV? I thought the HDHomeRun Duo allowed me to have 2 tuners running simultaneously. Am I doing something wrong?

Check my.hdhomerun.com to see what is using your tuners