When the phone does not show any indication of receiving a message, and the SIM card was recently transferred from an iPhone.
We have some customers who have reported that their group messaging didn’t work properly and that when we worked with them to discover why, the root cause was that they were part of a messaging group that was established when they had an iPhone. And the group was still trying to transmit messages via iMessage! The solution was for them to be removed from the group and then added again.
When the phone does not show any indication of receiving a message.
Most times this happens when an AT&T or T-Mobile reseller (MVNO) is used and the APN settings are not correct. To fix this, choose the correct reseller from the APN listing here: Settings > Connectivity > Mobile Network > Access Point Names. Please note that to select the button beside the correct APN (eg Consumer Cellular) you have to tap the little button using the touchscreen. If your reseller is not listed already, you need to add it by tapping the “+” button located at the top-right corner of the screen. After you have the settings entered, save them by pressing the “Menu” key (top-left button on the keypad) and then press the “Save” button.
When the phone indicates a message has been received and says “New MMS Message. Downloading”.
We’ve seen this happen on a Verizon MVNO (US Mobile). After a lot of troubleshooting, the root cause of the problem ended up being that US Mobile required “data” enabled on the line in order to download the MMS. (WiFi was not sufficient, for some reason. Adding “data” to the line fixed it).