1st off, thanks to those who have taken the time to offer up suggestions, insights and pointers in response to my (what sometimes seem) fundamental questions. It has been very helpful to get me to the point I’ve reached so far. Not quite there yet, but very close 
using OSMC w/TVH and there is 1 channel that TVH says is good, but somehow OSMC isn’t picking it up. Using the web interface into TVH, (Configuration/DVB Inputs/Services) the channels (main + 2 other digital ch.) show up. Then in Configuration/DVB Inputs/Muxes) the Mux shows up as OK in Scan results. Both have the mux/services Enabled checked. Yet, in OSMC/Live TV, the channel doesn’t exist.
What I have noticed is that this channel uses 2 different frequencies (1 in UHF and the other looks to be in VHF…which I believe to be fairly common). The UHF ch. scan shows good, VHF scan fails (since my antenna is primarily UHF, I’m not surprised). Both frequencies indicate the primary channel call sign with a “-HD” attached (which may not mean anything at all).
Any ideas what I may be missing here? Thanks in advance…