I had some issues using DIDLogic SIP as it was hard to get the right settings etc. and the didlogic website listed different server addresses (com/net etc). The right settings are very simple:
Service Provider Proxy Server sip.didlogic.net
Service Provider Proxy Server Port 5060
Outbound Proxy Server sip.didlogic.net
Outbound Proxy Server Port 5060
User Name 12345
Password typeyoursecret
URI <leave blank>
It should register like this.