Which plan are you on and Which phone are you using? MMS is supported on Koodo network. Just make sure you turn it on and you enable cellular data in your phone. 

I have the 10GB plan and have a Samsung S10. MMS is turned on my phone, I’ve used it with no problems until I went to Koodo. I can send MMS to individual contacts. If I start a new group it sends it individually not as a group, and if I try to send a MMS message in a previous group chat it comes up with the “Your SIM does not support multimedia messages”

If you were added in a group created by other people (instead of creating a group yourself), can you send and receive MMS from it?

Also, was group MMS messaging enabled in the settings?

No, still sends back as individual texts. I've had zero issues before I switched to Koodo. Can't be a setting on my phone. I literally took out old Sim put in new one and the issue started. 

Can you verify your APN settings match what are in the link below and are selected to be used on your phone?

https://www.koodomobile.com/en/help/setting-data-your-non-koodo-phone

Yes, APN settings match the settings in the link and is selected. 

Whenever you change your SIM, there was a new carrier settings need to be reset and changed. I suggest you reset your network settings first. Also, as I mentioned, check if your phone had MMS group was enabled.

Samsung devices also have that glitch for a while, someone wrote about it here https://thedroidguy.com/real-fix-for-group-messaging-not-working-on-galaxy-s10-troubleshoot-texting-issue-on-galaxy-s10-1101618

I have reset the network settings and MMS group is enabled. I’ve cleared Messages cache, I cleared the cache partition, only thing I haven’t done is factory reset the device.