3CX registration failed using VLAN on Cisco switch SG series.

[m.venturini1]

Dear Community.

I have the followng issue:

3CX system is the PABX voip we are using since 2 year. 

We have setup a VLAN for voip communication between IP Phone (Fanvill) and PABX. 

Al was working fine but recently after a firmware upgrade using that VLAN our phone are not more able to be registered to

the PABX, showing SIP registration failed on 3CX logs.

Rolling back to the previous firmware didn't solved the problem.

With both firmware same phones using instead native VLAN (Our office lan) are able to be registered

Current switch ( but all SG series are presenting same issue on our office) SG350-52P PoE

Current firmware 2.4.5.71

Unfortunately I'm not a cisco expert, please can you help?

Thanks

[m.venturini1]

Un update:

Re-setting the ports configuration from Trunks to Access and then againg from Access to Trunks solved the issue over the VLAN. 

What could be the root cause?

Thanks