Why can't I get MMS messages on my Lumia Icon (929)?

[Windows Central Question]

I have an Icon, and I'm using it on the Ting network. I used to be able to send and receive MMS messages (group messages and images), but now I can't.

I signed up for the Windows 10 tech preview to see if maybe it wouldn't have the problem, but even after using Windows 10 for a few months, I still couldn't send or receive MMS messages.

Tired of using a pre-Alpha OS, I backstepped back to WP 8.1... STILL can't send or receive MMS messages.

During all of this, I've been in touch with Ting several times, and they've been very helpful, but unable to solve the problem.

I know it's not a service problem.
I know it's not a problem with my plan.
It's got to be a problem with the phone.

Other oddities:
The Microsoft Support site lists settings that I don't see on my phone.
For example: "Go to Settings > mobile+SIM > SIM settings > SIM, and tap add MMS APN"
On my phone, "mobile+SIM" is called "cellular+SIM"
On my phone, in "SIM settings" I don't have the option to "add MMS APN." I only see "add Internet APN."

One last detail. The Icon was originally a Verizon phone, and Verizon claims they don't lock phones to their network anymore. Could it still be somehow associated with Verizon's network in a way that interferes with MMS traffic?

Everything else on the phone works. I can make and receive calls, I can access the internet over Wi-Fi, 3G, and LTE. I can send images in emails. Cortana usually works...

Any idea why I can't send or receive images or group texts?

 

[worldspy99]

Verizon locks down MMS on their devices like its nobody's business. You need to use WhatsApp or some other service. Sorry, you are going to be out of luck on this one. This is true for Android devices as well.

 

[dki378]

I'm interested in making the move to Ting with my Icon as well. Have you made any progress on this front? Or is this really a Verizon specific lock out?