WiFi calling wirh B535-232

Trying to trouble shoot why I'm having difficulty with Wifi calling.

Using Redmi 8T, dual Sim with ASDA(Vodaphone) and Three sims fitted. On my daughters Wifi, both work no problem. When at home don't come up unless I use am old MiFi unit to put up hotspot to link to primary Wifi, and can then switch back to main WiFi and maintain WiFi calling.

Have gone through as many trouble shooting ideas/tips as a can find, but to no avail. Only thing I haven't tried is a factory reset of the B535, but there doesn't seem to be option to save config, so I could restore my settings easily.

I welcome suggestions.

I have no experience of the B535, however I'm presuming your daughters wifi is using a different router?

Have you checked for an updated firmware for the B535?
Can you try turning On or Off UPnP to see if that makes any difference?

I remember buying a TP-Link router many years ago and could not get Wifi calling to work even with TP-link support saying there was no newer firmware, they replaced it with a better model and Wifi calling worked straight away.

It may well be a VPN passthrough issue with either the router firmware or a setting.

Yes my daughters is a completely different router.

The B535 seems to be on the latest firmware

I've tried UPnP, but to no avail.

Usually next to impossible to get firmware updates on these, especially if it’s locked to a network.

I wouldn’t suggest you go to the irritation and risk of visiting one of the .ru based firmware sites either. It’s either a simple setting or forget it and try another box.