Still no mms. 

Can you delete all APN settings profile in your phone and restart the phone again to see if it can help? 

If it worked several days before. There might be a glitch in phone settings. From your snapshot, APN was set correctly as per Koodo page 

Unfortunately I've tried resetting the APN and rebooting the phone several times over the last few days with no luck. I'll give it another try though. 

Deleting APN and rebooting phone did not fix the problem. 

You can try to reset network settings of the phone and see if it works. Also, take the SIM out and put it back. You could also test the network by putting the sim in another phone.

Resetting network options did not work, neither did pulling out and reinserting the SIM. I don't have another phone to try it in. 

Anyone have other suggestions? 

Try changing the ‘MVNO type’ from None to GID. The ‘MVNO value’ field should auto-populate with a two or four-digit alphanumeric value. Beside the APN type field, try entering default,mms exactly as shown - no spaces. Removing supl, or secure user plane location is covered by default in the default,mms string.

Remember to save any edits made to the APN settings. Since the settings are already saved to the APN, it is not necessary to reboot the phone, though it doesn’t hurt to restart the phone if needed.

Changing the MVNO to GID auto-populated MVNO value with 4B4F then removed supl from the APN type string and saved. No change in MMS failure to send or receive. 

Which phone do you have?

If there’s a second APN, try using one APN as the default and disable or delete the other APN. Try disabling Google Messages (if this is your default messaging app). Power the phone off and back on and enable Google Messages.  

If still no luck, it’s possible this could be a backend problem. In that case, please schedule a callback via Koodo Assist.

It’s a Xiaomi Mi 9t. The issue persists using both Google Messages, the native messaging app, plus all other 3rd party SMS messenger apps that I’ve tried. 

I did a little digging and came across this post on Xiaomi.EU’s community: “There is a conflict issue when you have Google Messages installed on the phone along with the Mi Messaging app that breaks MMS sending in both Mi Messaging and Google Messages. If you uninstall Google Messages, SMS sending will work again”.

Give this a try and see if this works.

Removing Google Messages and redoing Koodo’s APN one more time seems to have done it. I did try both of these things, but apparently not both at the same time. Thank you.