Any settings I've missed for WiFi-Calling?

Hi all,
I’m a new /e/ user with my Oneplus 7 Pro.
I am trying to get WiFi calling to work, but stumbled upon this strange error:

When I obviously have no cell connection (living on the country side) and the phone should switch to WiFi-calling (300mBit up and down on a Fritz with very strong connection), I’m presented a popup window telling me I should switch off airplane mode or connect to a WiFi:

Am I missing any settings or should I consider this a bug?
I am on the latest version of /e/ and connected to a fast and stable WiFi
Thank you for your help!

WiFi calling is set to be “preferred”.

first: pls, don’t double post ! It would be nice if you would delete one of both with same issue. thx

EDIT: thx, just seen, that your double post is delete.

now to your issue. I don’t understand it, sorry. With which app do you try calling over Wifi ?

Hi @debugger we had an issue for some users with nougat OS. Since you are on the Pie build it should work for you. Were you able to do wifi-calling with the same sim, network and data pack on your stock ROM. Checking to confirm if this issue started after switching over to /e/ OS

Hi @Manoj and @harvey186 , thank you for your replies and sorry for getting back so late, I was sick and in bed for the last week.
I switched back to stock ROM to confirm that the issue started with switching to/e/. Since using the stock ROM again I have no problems using WiFi calling with my device (same sim, network and data pack). As soon as I connect to a sufficient WiFi network my phone switches from cellular to WiFi calling. What I found interesting is that /e/ seemed not to recognize the state of flight mode or WiFi connection correctly (the popup told me to deactivate flight mode or connect to a WiFi although I WAS connected to a WiFi AND flight mode was switched off).

Hi @debugger thanks for pointing this issue. Pl can you raise a bug here. Mention details of which ROM and device you tested with. Also pl share the details of the stock ROM version and OS which has this feature.

Hi @Manoj, is resolving this completely dependent on @debugger submitting a bug report for you? In other words, will this be ignored if the bug report doesn’t get submitted by the end user?

hi @novacane the log reports help the developer identify the issue. In this case it would be interesting to know if wifi-calling is working on LineageOS builds for the same OS. wificalling is a bit difficult to test as it is not available in all locations or with all service providers. As such we have to depend on these logs and what additional details we have.

You should try

Dial code * # * # 4636 # * # * then choose ‘Phone Information’ and you shall see it the option

Source : @Ors on this topic