Call Apple and DEMAND to know if the geniuses running their servers have locked-out your devices. My wife had this ridiculously useless error "An error occurred during activation. Try again." on every device, except her iPhone. It turns out that Apple -surreptitiously and without any explanation- blocked her devices from connecting. Oh, her Apple ID worked fine for their unwanted iCloud by itself, but Messages and FaceTime would throw everything into chaos and refuse to connect with any real/meaningful alert (they sure can spam the Apple ID email with every other thing, why not to report an issue that requires a call to Apple). It's not enough to pay top $$$ for their stuff, but to lock people out of their Apple ID (logging-into iCloud still works b/c they want it to, but not on actual devices where Y-O-U want it to work) without any notice and with a stupid error that is meaningless (as per this and many articles like it) is tortious interference, plain and simple.
We wiped her iPad and MacBook Pro over and over for naught. I could get one of them connected to Messages, but then trying the other would throw them both in limbo again. In every instance, FaceTime on her laptop would accept the login but then ask about something in the keychain and pop back to the login screen without explanation (credentials were unflinchingly correct). Doing that would then ruin her access to FaceTime and Messages on the iPad, but the iPhone was always good. After a full day on the phone with a tech support agent who berated me (she was getting paid to hear my complaints, I was wasting time and money well beyond the call, which itself was too long), and then waiting almost 4 more days (2 "business days" so the weekend did not count), some higher support group simply unlocked her devices and they've been good to go since. Of course, when I asked why on earth they did this, she outright refused to give any explanation. So, all that wasted time and energy, just b/c a bunch of moronic Hollywood twits lost their nude pics to hackers b/c they used brilliant passwords like 12345, so now we plebs get to pay for it?! Seriously, Apple. The pendulum has swung waaaaaay too far into the ludicrous zone...
So, save your time troubleshooting - first call Apple and ask if their lordships have deemed you not good enough to access your own dang Apple ID on your own dang devices, and see if they secretly cut you off without any good reason or any compensation (or semblance of reasonable due process), lest you waste all the time and effort we did.
I can't imagine how anyone with less technical savvy would get out of this mess Apple made. Apple has totally abandoned the "it just works" mantra and even the simple (grand)mother rule in their testing and (morally and logically) bankrupt development decision-making.