SWM 8 setup with 5 H25 receivers. All showing "can't communicate with dish" On The power supply for the LNB, the light is flashing instead of staying solid. If I unhook the coax coming from the dish, light goes solid.

Bad power supply or bad LNB?

My understanding is that the light on the power supply means that it is within a valid voltage range. So, it going out can be because something is pulling too much current causing the power supply voltage to drop too low, there is a short on one of the coax in the system, or that the power supply is defective.

Unfortunately the answer is that it could be either, or a shorted cable.

Check for wires wrapped around the stinger on one of the coax. See this all the time when someone doesn't check their cables before hookup

Turned out to be a bad LNB

We had a few of those fail, all around x-mas last year. Why can't that kind thing fail more often in the summer.

This one failed today at a cottage at an exclusive country club, and it was reserved for a VIP that was checking in at 5:00. I have no idea who the VIP was, but I do know that usually, the club tells me names. Probably second worse scenario to failing at Xmas.

We had this happen on a multistory setup with splitters on each floor and an amp about halfway down the stack. The device that locks down the voltages and signals going to the LNB was bad. When one channel on that was disconnected, the light stopped blinking.

The blinking light does indeed mean that something is bad. It's a matter of troubleshooting from there to pin it down, the problem usually being that you don't have an entire second set of parts with you when you run into the problem.