Mango office: Failed to connect to the authentication service. What is the problem?

Question

Telephony

Some of the employees could not log in, gave out a subject. Mango talker came in, but the calls did not go, although the SMS was sent. After half an hour, everything worked by itself, but I'm wondering what to do next time in order to speed up the process of returning to work?

I searched in Google, but even I am not satisfied + I don’t rummage in the administration, but there it’s only tricky.

And what other services for calls can you recommend? It is the office version that is of interest, so that the calls allegedly come from specific numbers.