All instances using only Google DNS. It is not possible to activate 3CX license with another DNS server. There are temporary problems with 3CX upgrade server probably.I updated 2 pbxs about an hour ago which are hosted in my own Google Cloud account and everything went smoothly. Maybe if you use Google DNS? (8.8.8.8)?
Dashboard shows version 15.5.8801, I assume its the latest
Founded in 2005, when VoIP was an emerging technology, 3CX has gone on to establish itself as a global leader in business communications.