[Freeswitch-users] Only Eutelia not working on NAT

My freeswitch is working fine behind a NAT with 12voip, sipgate, voipcheap, VoXalot as my router support UPnP. Recently, I have applied some DID numbers from Eutelia.it and tested the account with x-lite. But when configured to FS, it can only make out-going call and fail to receive any form this gateway. In the meanwhile 12voip,sipgate are still working well. I tried many parameters but none of them works unless the router was removed and FS connected directly to public IP. It is quite strange for only a single gateway fail behind NAT, while all others is fine.