Hello HappyDog,
Welcome to the community!
I understand you have checked the APN settings, however, have you verified the MMS settings are included? You can verify the correct settings here.
Since the phone is LTE-capable, it should be using ltemobile.apn. It's possible that since the update, your phone now relies on its internal database of APN settings. Unfortunately, that database is not always accurate. It appears as though those APN settings included in the internal APN database does not include MMS information. Other community members have similars issue with their unlocked phones (see here and here and here). You might consider trying the fido-core-appl1.apn to see if you are able to send and/or receive MMS as the database appears to have that APN correctly listed. Unfortunately, using that APN would not allow connecting to the LTE networks.
If you are able to edit the ltemobile.apn, adding the MMS settings should correct your issue. If you're not able to edit the APNs, are you able to add a new APN with the inclusion of the MMS settings? If you are unable to add an APN, your options are more limited (see here). You might consider contacting the manufacturer to see if they can edit the phone's apns-conf.xml file with the correct settings.
Hope this helps 😀
Cheers
