Block wan request is on. 3CX system

I am trying to connect to my 3CX PBX on an amazon ec2 windows server 2012 instance. I have created the security group, and added exceptions in the firewall. The firewall checker in the 3CX control panel says all ports are open and it should be working. However whenever I try to connect a device I get the error:

SIP request (REGISTER) from xx.xx.xxx.xx was rejected. Reason: block WAN requests is on.

Thanks in advance for any help.

I've seen that error when 3CX and phones were on different LANs. Have you tried unchecking Extension > Other > Disallow use of extension outside the LAN?