Refer here for background: https://productforums.google.com/forum/?utm_medium=email&utm_source=footer#!msg/voice/0KyY1l6rhpc/S2...
Following the discontinuation of MMS/SMS functionality in Google Hangouts, Google Voice can be used to send, but not receive, MMS messages: photos, group messages, etc.
This only occurs in Google Voice on Sprint - users of unintegrated Google Voice can both send and receive messages.
However, if you port your number fully over to Google Voice, your line is automatically cancelled. (Which I don't want: I've been with Sprint for 10 years, like my local network coverage, like my plan...)
Is Sprint currently working on resolving these issues, or is there a usable workaround (create a second line on your account, for example, and swap your original number with it, and then port the original number from the second number over to Google Voice, cancelling the second line? Maybe? Any ideas?)