[Sophos UTM9] SnapChat text is not working on iPhone

I have installed the Sophos UTM9 firewall that released for home use only. This firewall is pretty good. Actually, the firewall is one of the best firewalls in my 25 years of IT experience. It has so intuitive menu and options.
It took about an hour to install it on our VM lab environment to complete an operation.
A few hours later, my son said the SnapChat text was not working for a few hours back. Oops~
But Android phone is working just fine, but iPhone ??? Why???
Actually, SnapChat text on iPhone worked with LTE.
Um……

Here is how to fix.
Disable “Enable Pharming protection” under Web Protection / Filtering option / MISC.

I hope it is informative for you.
My son is happy now.