My ZTE Max XL recently stopped accepting MMS downloads from specific people in a group text that I have been exchanging messages from for a couple years and has stopped sending my messages. Other contacts are completely unaffected. I have deleted and re-entered the names of those affected, in addition to clearing cache and data and re-setting APN, and it makes no difference.. When I turned off my wifi, some of the messages came through. Any way to get it back working with wifi on?