>60 TCP handset connections causing Not Reg on handset in Windows-related Topics Posted October 8, 2015 · Report reply The issue was resolved by upgrading to PBX version 5.3.0. The issue was a constraint/limit that had been imposed by a new compiler that was used for version 5.2.3. This specifically limited the number of SIP connections to 64. We upgraded to version 5.3.0 and we've not had a repeat of this problem. I can also recommend updating the Snom 300 firmware to version 22.214.171.124, as this reinstated the call pickup and the ability for a user to change the ringtone on the handset.