You might not have VoLTE activated on your account for some reason. How recently did you port over? 

May be unable to verify your geographical location. Some settings in your phone could disabled location visibility. WiFi calling only works in Canada

I’m in Toronto, and I can’t recall or find any suspicious setting that might have disabled the location visibility.

The VoLTE access add-on has to be added to your account for Wi-Fi Calling to work. The add-on may have already been added. 

To check, log in to your Self Serve account. Click/tap the Self Serve tab and select Mobile services. Click on My add-ons and check that the VoLTE access add-on is visible in the list of add-ons. If the VoLTE add-on is not visible, we can flag a rep to add this to your account.

If the VoLTE access add-on is visible in your Self Serve account and you cannot enable Wi-Fi Calling, the next step is to schedule a callback via Koodo Assist. Enter “schedule callback” (without quotation marks) into the chat window and follow the prompts. At the start of the callback, explain the problem and ask to speak with a tech support agent.

Thank you all. I do have VoLTE add-on in my Self Serve upon checking. But Wi-Fi calling doesn’t seem to be working properly. The enable switch in my phone setting sometimes turned itself off for some reason (WiFi was present and signal was strong), and I wasn’t able to enable it when the issue happened. I will try Koodo Asset when that happens. Thanks again.

I think there was a bug with WiFi calling of Android devices. Sometimes, you would have to reactivate wifi calling again. 

Also, Koodo wifi calling prioritized "cellular signal" over wifi signal, so wifi calling would only show up when the cellular signal was bad and your internet ISP didn't block it.