Disconnect after 32 seconds of SIP talk time

Hello, I have tried to move away from Zoiper to a community driven solution which is Jitsi.
I have no NAT or other router problems as Zoiper is working however it’s handling of Audio streams on my Laptop is very poor. I was glad to test Jitsi and find the Audio Quality superior, however using the sip.fcn.pl service I find all calls disconnect after 32 seconds which possibly point to SIP ACK signal not getting through … Now there are many options in Jitsi for keepalive possibly some I do not know about …. If anyone knows a possible solution to this problem I would kindly appreciate sharing it with the Community.