Upgrading from V12 to V17, can't get it to work

We got a new client last year, most of their equipment is stuck far in the past. Trying to get them up to some kind of modern standard for security and compliance. One of the last things we need to do is get off this ancient version of FreePBX and move to the current one. The guy who originally set this up 6 feet under now so he isn’t much help either lol.

The situation:
Out SIP Provider is updating to require attestation for shaken/stirred protocols

The Upgrade:
Made a backup on the V12 box, exported it with SCP
Setup new box (VM), follow the setup guide on the freepbx site for installing Debian 12 and then FreePBX. Restore the backup, informs me some things are no longer supported and must be converted, most of the we seemed to say this would be fine and to proceed.

Post Upgrade:
After reviewing both systems the settings seemed to all come over except the TFTP boot files so I moved them over manually and then proceeded to schedule a test day for the swap (today).

The swap:
After shutting down the old box and booting up the new VM nothing works at all. Internal phones don’t register, can’t call each other or anything, can’t call in or out. Errors saying SIP couldnt connect, retrying in 60 seconds, but it just loops forever. I tried a ton of stuff, checked time of the VM (it’s accurate) traffic tracing, review logs. I can’t figure it out for the life of me.

Potential solutions:
I don’t even know where to start. The more I learn about PBX, SIP etc the more I realize there’s a lot to it. The RFC changed from 2833 to 4733 but they say they are compatible so I don’t think that is the issue. I’m not sure setting up from scratch is feasable or not, or if it will even resolve any of this. I can provide logs etc but I wasn’t sure what you would want so if you can tell me what logs you want I will provide them ASAP.

Thanks in advance for any and all help

How many phones are there?

I don’t think the tftp server is enabled by default anymore. Try to register by http or https instead. Or enable tftp under system admin>Provisioning protocols. If the phones don’t register, calls won’t work.

Also check the firewall and make sure the local subnet is added.

Thank you so much for your reply. I am back on site at this client today and will try enabling TFTP after they are closed and do a test. They use a bunch of ancient phones so I didn’t want to change the config for the phone side if possible (switching to http or https). Many different phones from different brands.

To add a little bit, my main concern is the outside calling in, it never registers the SIP trunk, the provider says its not locked to the old box or anything, just IP. Box has the same IP, not sure where to start with that part of it either, the provider is not any help with our end. And the client is stuck with this provider for 3 more years. When you call in with the new PBX running it acts as if the line is disconnected