I wanted to keep my above comment to the data only, so I'll post this here: "Equipment Failure" can cover just about anything. I think the "gut" reaction the public might have here when hearing that phrase is that it was physical equipment, but really it could have been software, network linkages, really anything. I hope the real cause here doesn't get buried somewhere in lack of follow up.

Also I really wish I'd been awake when the hotline was active (# was in the full notices linked) so I could call in and see what they were talking about as a silent observer. I can't tell from the context if that was a general status hotline, a failover service to provide the same data NOTAM would have done (though if that were the case then grounding flights wouldn't have been necessary) [1] or discussion of the actual problem and specific efforts to resolve.

[1] Well, only if it was a more benign & limited cause that wouldn't be expected to spill over into other systems. If the nature of the problem included the possibility of a malign actor then other vectors of attacks would not have been (and maybe still aren't, if that was the source) off the table.