Please check the firewallcheck und report back
Windows Server 2016, Standard Annual 16.06.655Please provide more details on your 3cx setup
https://www.3cx.com/community/threads/information-to-provide-when-requesting-help.67558/
You need to upgrade to V18, as 3cx have changed system settings i.e. activation servers.
The main issue you have is server 2016 is not supported any more. - https://www.3cx.com/docs/manual/phone-system-installation-windows/
Step 1: Check System Requirements
The following Windows platforms are supported:
- Windows 10 (Pro, Enterprise)
- Windows Server 2016 (Standard, Datacenter)
- Windows Server 2019 (Standard, Datacenter)
My mistake, I read your post as Server 2012
Thanks, all good )Backup 3cx with fqdn and license
move the backup to a local machine
uninstall 3cx
reboot server
install v18 , using restore from backup option - use the backup from step 1 https://downloads-global.3cx.com/downloads/3CXPhoneSystem18.exe
Founded in 2005, when VoIP was an emerging technology, 3CX has gone on to establish itself as a global leader in business communications.