In my general experience, most of the "can't connect, even after updating" are trensient.
Once I update to the latest version, I always end up eventually having access again.

Re-registering doesn't seem a very good idea.
WhatsApp probably have code to detect too many attempts at registering same number again.

(Because I strongly suspect that's the behaviour WhatsApp expects from SPAMers. Thus, by trying to re-register at the slightest connection problem, WhatsApp might automatically flag you as a SPAMer.
Hence the weird answers from the WhatsApp costumer service: "Your number isn't a real mobile phone, but a VOIP number" or "Please send proof that this a mobile number you own by sending a picture of your SIM card and a copy of your phone bill", etc.)

Waiting out the outage and updating to the latest version seems to work better (never got rejected).