Ever since switching to xfinitymobile for iPhone XS, SMS and MMS do not send to non-iPhones.

I've never had an issue with this before, but now whenever I try and send a text to someone who doesn't also use an iPhone it fails to send. After a quick search, I found that this is apparently been an issue for a lot of people but none had a solution. I tried going through all the redirects from the xfinity support number, but there's no automated option for issues like this and I hit a dead end. Why is this happening only to people who switch to xfinitymobile? Why is it even happening in the first place? I don't even know where to start to try and solve it on my own, so I'm hoping someone can help me fix this.