Do you have MMS issues with Cricket Wireless? These settings below worked for me and I tried just about every different setting on various discussion groups before this one finally solved my problem. The issue is, reboot your phone and the problem comes back. I am using a Pixel XL running Oreo 8.1. It's stock Android, no rooting.
I got the typical responses to stop using the built in texting app and install Textra. I tried Textra and it did not solve the problem. Plus Textra would not even indicate you received a MMS that it could not download, so you have no clue someone is sending you a MMS message when using Textra. So I uninstalled it.
Anyways here is the fix that works for me. You need to add a new APN. Follow these steps:
Pull down the notification bar from the top of the screen
Press the gear button
Select Network & Internet
Select Mobile Network
Select Access Point Names
Press the + key to add a new APN
Use these settings below and make sure you press the 3 dots in the upper right corner and select Save:
(Make sure the radio button is selecting the new APN you just setup)