My phone won't ring

There's no public outage page for Koodo that I'm aware of, unfortunately. Is your mom on an iPhone as well? Two lines behaving the same way narrows things down a lot.

Two things I would check before anything else. Live Voicemail on iOS can interfere with Koodo voicemail, and that matches what you're describing, dead air on the caller's end and then a failed call. Try turning it off in the Phone settings. As well, make sure Focus/Do Not Disturb isn't on.

If nothing changes after doing so, you can put your SIM in another phone and see whether the problem follows the SIM or stays with the iPhone. More tips here https://www.koodomobile.com/en/help/im-not-getting-any-network-service

Thanks for this. I turned off live voicemail. Also, focus is off. 

I just tried calling my phone repeatedly using my wife’s (Bell) phone. Still no response.

I have an esim. I do get 5g internet just fine.

Another thing I noticed. I call my wife’s phone and it takes a LONG TIME for her phone to ring. I just counted to 26 until her phone rang. 

From your description, it seems your location doesn't have good signal reception. Have you tried to enable wifi calling? 
How about other people living near you. Are the experiencing the same issue?

Hm. I was able to make calls with my wife’s phone. And data is fine. I am at home where the signal is good. Unfortunately this has been going on for a while. Even in downtown toronto. My phone takes forever to dial another number, too. 

I’ll try a koodo kiosk. 

It is possible there is some sort of interference in your home. Have you tried enabling wi-fi calling on your phone? That may help resolve the issue. https://www.koodomobile.com/en/help/wifi-calling