5g hub ZTE mc888 won’t allow WiFi calling

[Rural]

We have recently switched to Three. We switched from the standard broadband to the 5g hub because we are very rural and our highest speed on the line was 5mb. With the hub we are getting the fastest broadband we’ve ever had. But here’s the problem: it won’t allow us to use WiFi calling. We rely on WiFi calling because signal in the house is awful (old house and very thick walls). WiFi calling worked for us before but won’t with this hub. Can anyone help us with this?

[Hagadol]

Using my iPhone O2: On all other Wifi networks, if I try to force Wifi Calling, by turning on Airplane Mode within less than 10 seconds it switches to WiFi Calling.  With my Three 5G Hub it has occasionally turned on in the last week, estimated about 20% of the time, whereby before the last week it never did.