Cannot connect over Optus 4G
We have had a number of customers report that they are unable to connect to MaxoTel over the Optus Wireless 4G network.
This is an issue with the Optus network interfering with SIP traffic, which affects both MaxoTel and other providers.
Unfortunately there is no known guaranteed workaround for this issue at this time, however requesting that Optus enable 'VoLTE' on your 4g service may improve performance.
The recommended solution is to switch your 4G connection to another provider, such as Telstra, which has been shown to work.