maybe try calling at&t support? sounds like some configuration thing on their side.

Been on AT&T for five years and I have not had any problems like that.

I'm on Android also.

My suggestion would be to consider resetting your phone or at least finding some way to reset your settings.

You may not have your SMS or MMS settings set correctly.

If you're on Android you could also try switching over to a different text app, like Textra.

The pro version of Textra is a couple of dollars, but I find it far superior to Google messages in every way except for the whatever RMS or IMCP or whatever the new media texting thing is for Apple compatibility.

Just keep in mind, the better cell carrier heavily depends on where you are. Verizon in Tucson is the worst cell provider, and T-Mobile has been better than AT&T overall (except in the desert).

Are you texting someone on T-Mobile by chance?

On AT&T and Android. I use Signal as much as possible because it just works sending and receiving anything (text, image, video, URL's) whether I am using cell, wi-fi or Starlink. When I am on Starlink with no cell data available I can usually send or receive a plain text but if I attach an image or have a URL in the text it regularly fails to send and throws an error notification.