I've tested it myself and everything is fine.
Have you got the right APN settings?
Yes APN are right. I can send MMS.
What ROM did you had before this?
My phone was global 12.0 and I flashed with TWRP 3.7 the CN 12.5.
I have Portuguese dictionary in keyboard not sure if this affect.
I tested with Gboard and SwiftKey with same results, Google Messages and Textra the same.