After further investigation and updates to the server, the Mobex Desktop solution has been moved back to phone.sip2sip.net from beta.phone.sip2sip.net. Whilst both services will continue to work for some time, should your customer experience any issues please ask them to:
1) Type phone.sip2sip.net in the browser
2) If the browser returns to phone.beta.sip2sip.net, try the Ctrl+Shift+Del operation to delete the cache browser data and then type the address again.
Thank you.