WiFi Calling Issues with TZ270
We are having a persistent issue with a SonicWALL TZ270 that we installed about two months ago. The customer complains that they can't send or receive calls from their cell phones while connected to wireless. We have gone on-site and confirmed that when you try to call out it just sits on the call screen and never connects. Inbound calls go straight to voicemail. Happens with both Androids and iPhones. Here are the troubleshooting steps we've taken so far.
1) Updated the firmware to the latest release (7.0.1-5111) No change
2) The issue happens with both iPhones and Android. Despite these, we tried enabling "Preserve IKE Port . . ." setting per this KB article: https://www.sonicwall.com/support/knowledge-base/unable-to-call-via-apple-wifi-calling/170505913456806/ No change.
3) Per support, we've tried disabling DPI from LAN to WAN zone. No change.
4) Today, we pulled the SonicWALL out and hooked the old ZyXel USG20W router back up. We are going to have them test for a week to see if it stays consistent, but, so far, wireless calling works just fine on my phone, inbound and outbound. They also confirmed that they weren't having the issue prior to the SonicWALL being installed.
Any one else run into this issue and have any thoughts? I've had years of good experiences with SonicWALL, but I'm pretty embarrassed having to apologize to my customer for this brand new device we recommended that's become such a headache at his office. I'd appreciate any guidance from the community.