Welcome to the world of Switched Digital Video.
First lets find out how SDV Works. SDV works similar to on-demand or say youtube (in laymans terms) There is a server at the "hub" and a set amount of "channels" 6mhz wide carriers)
Normally what happens is the BHN sends out every single channel on a carrier at once. 1 Analog channel takes up an entire "carrier" on its own. 10-15 Digital Channels can take up a single "Carrier" and up to 4 (depending on compression and activity ala sports vs say static images) HD Channels per carrier.
That means cable companies are limited to the number of channels they can offer based on the available "carriers" Since most cable systems (BHN being one of them) Are 750mhz systems (BHN Tampa I believe has upgraded to at least 870 maybe even 1ghz) And each Carrier is 6mhz wide and the first 50MHZ is set aside for return, that leaves a limited number of free carriers.
So what the cable industry has come with is a simple solution called Switched Digital Video (SDV) What it does is instead of sending out EVERY channel it only sends out the channels people request. So this way they can offer "100s" of channels but not need the space for them. As they only take up space when someone watches it. It "streams" the channel to the customer as they tune to it.
The problem is however when to many people want to watch to many different channels at once. The least popular channels are the ones on SDV however there are channels like starz etc on there also.
BHN was not at all prepared for the high demand and strain on the system, as they put way too many "nodes" (A node normally feeds a neighborhood of up to 500 passings or fewer) per "server" So what they have begun to do is upgrade and change this.
So as they upgrade it will be 1 for 1. 1 Node per server, thus giving way more space and eliminating that "cant see channel at this time" message. They are doing this at the same time of preparing the hubs for DOCSIS3 (wideband / lightning) but it is happening. They are also physically splitting several nodes based on "box" count (how many cable boxes a node feeds) Where as before node splits were only done based on modems (because only modems used "bandwidth" and needed free space) Now Boxes work similar in theory to the modems and traffic is important to monitor.
So nothing you can do or BHN really until the upgrades and node splits are done. The only thing you can really do is just keep trying the channel and wait till you get a free spot.
One problem is people will turn on an HD channel and when done watching TV turn off the TV but not the box. So in turn their cable box is still using that space for the HD channel even though no one is watching.
Its a problem ALL cable companies are running into and it simply requires them to upgrade the backbone. Which BHN is doing. Trust me I know
Hub techs are working 30-40hours OT a week to get the network upgraded. It can only happen so fast as its a lot of work to do, and it has to be done in stages to limit impact. And to catch problems before you get to far along.
Anyway a bit long winded but hope it helped.