Well that is weird. My initial thought is maybe there is something going on inside your pixel that might be shorting your sim? But this is just a guess. Do the sims work in another phone?
When you mentioned the new sim didn't work, what was the status showing at the top right of the screen. Did it say “no sim” or “emergency calls only”?
Also, I assumed your account was in good standing and active?
Hey folks,
My old SIM stopped working randomly. It was pretty old so I figured it had just lived its life.
I got a new one to replace it, activated it and switched them. It worked for about 10 minutes and then suddenly stopped.
I can’t phone Koodo to ask because, well, no SIM card. 
I have two questions: Is there such thing as email support for Koodo?
And, does anyone have any idea what might have happened here? Has anyone experienced this?
(In case it matters, the phone is a Pixel 6)
Thanks!
megan
Did you try restarting your phone? What about resetting your network settings? Have you looked into your APN settings as well? https://www.koodomobile.com/en/help/setting-data-your-non-koodo-phone
Hey everyone, thanks for the answers!
A bit more information...
I am leaning toward it being something to do with the phone.
My old SIM from previous phones lasted in this new phone for about a month, but started periodically dropping service pretty early before giving up the ghost completely.
The new SIM, the one that worked for about 10 minutes before tanking... It did work a second time all of a sudden briefly for a wee bit last night. And now is not working again.
So, yeah, I think it is phone-related.
I've connected with the store I bought the phone from and am going to exchange it for a new one.
Thanks everyone!