Restore of Backups
If you install 3CX V15 and you use license key ABCD-ABCD-ABCD-ABCD, do NOT RESTORE backups with another key from the management console to this installation! The installation and FQDN selected at install time is bound to the license key you enter in the PBX Configuration Tool Command line Wizard.
If you restore a backup, you will activate 3CX with the license that is inside the backup. This means that the installation will have FQDN problems and conferencing will not work. Replacing the license key or importing a backup with a different license key requires a reinstall of the PBX!