When you tried this, was wifi enabled or disabled.
I found that when wifi is disabled the success rate of activation is much much higher.
Also, make sure there are no restrictions to texting international numbers.
iCloud needs to send a text message to Apple servers in order to get activated.
I sign out all the imessage and facetime on my iphone 6s+; ipad and macbook air, as well for the iphone 5 which can't be activated
Reset network from the iphone 5, reset to factory, register as new iphone (which luckly I only use this phone for my banking apps), reset again for the network, re-sign apple id, re activate the imessage/facetime and finally success
Now both my phone number and 2 email addresses all registered