Many thanks once again. I think I'll call Verizon. If I start messing around on my own, they might accuse me of messing it up. I think they should take full responsibility for fixing it.
Yes, my account isn't open. At least it isn't supposed to be. The building offers free WiFi, but I wanted better security than that offers.
The specific wording in the diagnostic report was "congested channel". The files are still on my computer, if they want to see them.