I've already solved this issue, but want to post my solution for anyone who may have had a similar issue and came here from a Web search. The screenshots were from me reproducing the issue.
My issue
When I set up Tvheadend, I had 2 tuners each across a WinTV HVR-2200 and HVR-2215. I then swapped out the HVR-2215 (to use on a different Tvheadend server) with two more HVR-2200s, making for a total of 6 digital tuners across 3 cards.
I then have 6 tuners available, but during some DVR recording tests, I noticed that Tvheadend would only record from the highest numbered tuner (#6), while recordings from other DVB-T multiplexes had an error icon and the status indicated was ‘Waiting for stream’.
Troubleshooting
As part of the troubleshooting process, I disabled all recording schedules and Autorecs to allow me to freely restart the server if needed. I then created timers for one HD TV channel each on each DVB-T multiplex (mux) in my area (the area I live in doesn't yet use DVB-T2) to test and see if it worked. The issue was still present, and I took this screenshot during my troubleshooting process.
Solution
I noticed that when setting up Tvheadend, the user is asked to assign tuners to networks, however, for tuners added after the setup was completed, I forgot that I had to do that and Tvheadend didn't automatically assign them, as you can see.
Once all tuners were correctly assigned to (in my case) ’DVB-T Network‘, I tried enabling the test recording timers and was successfully able to record from all 5 multiplexes in my area.
