Help Can't send MMS on RingPlus with my Sprint Galaxy Nexus

[paroots]

I have not been able to send MMS messages on my Sprint Galaxy Nexus (SPH-L700) with my prepaid carrier RingPlus. I can do all of the following without issues:

• send/receive SMS messages
• receive MMS messages
• place/receive calls
• browse WiFi
• browse mobile data

Here are some things I've already done:

• update Profile
• set MMSC URL
• perform factory resets
• install APN zip file found here: [FIX] Ringplus APNs - Confirmed 4G - xda-developers
• install APN zip file found here: post #32 of [TING] Flashable ZIP - Fixed LTE for Android Pg 4 | Galaxy Nexus > XDA

I'd be interested in hearing from other users of this phone on RingPlus.