BYOD device to Ting? Using Google Hangouts for SMS/MMS? Your MMS not working? System has your MMSC URL correct, but it wasn't correct when Google Hangouts SMS was turned on?
1. Turn OFF SMS in Google Hangouts under its Settings
2. Check your MMSC URL is correct
3. Turn ON SMS in Google Hangouts under its Settings
Apparently, Google Hangouts uses its own APN settings, but on CDMA phones, it will pick them off from the system when SMS is turned on for the first time.