But i presume i still not in the right version to make a backup and recover my config in version 18 ?
You cannot upgrade from v15 straight to 18. You'll have to go through v16 first.
But different think as changed into the console.
If you're running 15.5.15502.6 then taking a backup and moving to 3CX v16 should be just fine. Just to confirm what version do you see in "Dashboard >> Information >> License"? If it's 15.5.15502.6, do the following:
1. Take a full backup and move it away from the machine.
2. Shutdown the machine.
3. Deploy a new one using the
3CX ISO for v16.
4. Use the backup during installation to restore your config.
5. Once the PBX is up and running in v16 and all is well, go into "Dashboard >> Information >> License " and confirm you are now running 16.0.8.9.
6. If you are indeed running 16.0.8.9, take a full backup and move it away from the machine again. Then click on "Updates" in the upper-right corner of the Management Console and check if you can see an option to upgrade to 3CX v18.
7. If you can perform the upgrade. This should not only upgrade 3CX from v16 to v18 but will also upgrade the OS from Debian 9 to Debian 10. That said, it might take longer than a normal 3CX upgrade.
8. Once complete, check the version again, it should read 18.0.1.237. If so, you are now running the latest version of 3CX.
Notes:
• I'd recommend undertaking this task during out of office hours since downtime is inevitable and also so that you have enough time to revert/troubleshoot should something go wrong.
• Make sure to save and keep all backups taken in a safe location until the whole process is complete.
• Shutdown any old machines when done with them and do not uninstall 3CX or delete the old VMs until you have confirmed everything is in order with the new one(s).
• Before proceeding make absolutely sure that the hosts can resolve and reach activation.3cx.com and activate.3cx.com.