I have a Samsung Galaxy S10+.
I have gone through the troubleshooting process with my carrier many times but to no avail. My APN settings are correct and I can send and receive MMS texts using the default texting app built into Android 11. Unfortunately, if I use any other app: Textra, Google Messages, Chomp, etc., I cannot send MMS texts (SMS texts seem to send with no issue). My carrier said, after these numerous tech support sessions, that it must be the phone. I cannot imagine that the phone could be the issue if SMS works but MMS doesn't, except when using the default app.
Can anyone shed some light? Any help in getting this resolved?
That's an issue with carriers such as H20 wireless. But sometimes if you insert a Tmobile sim and remove it. Your phone may start sending MMS via Google voice. I don't know the technical explanation but I think the phone is not compatible with such carriers and apps
Try using the SIM card from someone else that is on the same carrier. If the issue resolves, you need a new SIM. If it doesn't then at least you will have confirmed it isn't on the carrier side.