It looks like MC only found one physical tuner device that has two tuners in it. So one of the dual tuners. But it couldn't connect to the tuner it tried to, hence the error you received. The underlying error was;
0055297: 11260: TV: CGenericHDTV::BuildUpstream - 0x2a9a2684d40: Cannot load tuner device and connect network provider hr=0x80040154
In fact, your system specs show one single tuner device, one dual tuner device, and the Prime as a triple tuner device. But it doesn't identify the models. At least not in terms I understand.
Could you share the model numbers of all the HDHomeRun tuners you have? Thanks.
It also looks like MC might be trying to run an EPG job, which would prevent a Channel Scan from working. If you have been loading a MC Library Backup that has EPG Profiles, could you disable the Profiles, restart MC, and try the scan again?
Beyond that, I can't see what the cause is in the log. Maybe Yaobing could see it. But it is strange the MC doesn't appear to see all three tuner devices.