We had a customer using T-Mobile iPhones and Android phones to connect to an LQ-Agent IC. The Android phones would connect without any issues, but the iPhones would not. After some troubleshooting done by our Technical Support Engineer and the customer, the customer came back with the following:
"..So Apple has slowly forced app developers to move to IPV6 only networking within the phone... Cisco Meraki MX firewalls do not pass IPV6 VPN traffic just yet....Android hasn’t been moved to only passing IPV6 just yet from what I am reading" (May 2019)
Similar issues could be related to firewalls/routers not passing IPv6 traffic. Clear-Com has used a Cradlepoint router to help troubleshoot this type of issues.
For additional assistance, please contact Clear-Com Technical Support