Now iMessage won't reactivate
I followed the instructions, including switching iMessage on and off. But now iMessage won't activate again on my MacBookPro.
I get a warning window "iMessage Activation. Could not sign in. Please check your network connection and try again." Well, my network connection is OK. I have Internet on all my devices, incl. on my iPhone 5. Facetime works also (it is activated and shows my email address. iMessage is no longer activated and I can't, no matter how often I try.
Receiving and making cellular calls via my MacBookPro also work.
So my iMessage (on my MacBookPro and iPhone) are now regular SMS messages (blue clouds instead of green). It worked before, now it doesn't.
And, of course, what started it all: receiving and sending SMS on my MacBookPro, don't work.
Now what?