Can't get firewall checker to pass. Watchguard T20W

[[email protected]]

Watchguard T20W 12.7.2.B655803
3CX 18.0 Update 3 Build 461

Static external IP.
STUN not used.
FQDN resolves correctly.
SIP Trunk Carrier - siptrunk.com

Windows Server 2019. Not virtual 2 local internal IP One for small intranet, One just for 3CX.

Configured per Watchguard XTM instructions on this site. All this is clear and set up as shown without issue. I have several public static IPs on firewall. One exclusively for 3CX correctly resolved by FQDN.. Checked on 8.8.8.8 to eliminate internal / external issues.

Internal DNS resolves FQDN to dedicated internal IP.

Everything appears to work correctly. Calls placed and received. 3CX phone on Android works fine internal and external..

Can't get firewall checker to pass. Error: 'full cone test failed'

Any thoughts where to look next?

Thanks

 

[ChrisC_3CX]

If you're only getting the "Full cone test failed" it usually means you are failing Test 2 described in this guide: https://www.3cx.com/docs/firewall-checker/
I suggest giving it a quick read as it describes how the firewall checker works and hence should provide some insight on what configuration on your firewall may be preventing a successful pass.

Also, is this the guide you followed for the firewall checker: https://www.3cx.com/docs/watchguard-xtm-firewall/
I do recommend going over it at least once more just to be certain you have not missed anything.