Upgrade to V16 no detection of new phones

[vintegrity]

Hi, I've been running into a confusing problem since I upgraded from 15.5 to 16. I backed up 3CX then uninstalled 15 and installed 16 (I didn't manually erase any directories) then restored the config and everything seemed to be working properly. I recently noticed that added phones are not being detected. The phones are reset Yealink T20p on the latest firmware (yes I know they are older but they were auto detected before the upgrade).

The config (hasn't changed)
Yealink T20p on latest firmware
The server has 2 network interfaces 192.168.0.x and 10.10.100.x with the windows firewall disabled in all cases.
The phones are attached to the 10 network and the second NIC is on the 10 network with no gateway set and plugged into the same switch and properly receive DHCP as they always have.

Things I've tried:
Reset the phones.
Added DHCP option 66 (Never needed it before but figured I'd try it)
Reconfigured some phones that were already attached and they reconfigured and reprovisoned properly.
Disabled the setting in 3CX ( Enable PCI compliance SSL/SecureSIP Transport and Ciphers)
Firewall checker passes all tests,
Checked provisioning directory to make sure no configs exist matching the MAC of the phone I'm trying to detect.

I just don't know what else to try since everything is on the same local switch and almost everything works properly. I have internal and external users and everything is working except the detection. I don't have any newer phones to test with but I suspect that they would be detected either. Is there anything in the 3CX upgrade that might possibly be causing this?

Thanks for any help in advance.

 

[diamond9]

Hi,

Since you have 2 adopters have you looked through this article?

https://www.3cx.com/docs/plug-and-play-ip-phone/

 

[JohnS_3CX]

Hi @vintegrity

This appears to be a multicast issue, if the phones are not on a network that the PBX is registered to listen for multicast then the PBX will not see their message. Take a look at the article linked by @diamond9

Also, what OS version are you running the PBX on?
https://www.3cx.com/docs/manual/

 

[vintegrity]

It's running on Server 2012. Thanks for the article I'll double-check and see if something might have changed for some reason.

 

[JohnS_3CX]

We recommend to upgrade your OS as soon as you can so you can install V16U5.

Server 2012 will no longer be tested/supported due to the fact that it does not support HTTPS/2
https://www.3cx.com/blog/releases/apple-push-update-windows/

Let us know if you have any questions before you proceed, we will be glad to assist!