No reconnection after signal loss? Here's why.

SOLVED

The phone chose another network that has signal. This other network informed the phone that all services are not allowed. After receiving this information, the phone will consider the 4G-capable SIM invalid until the 4G-capable SIM is removed or the phone is restarted somehow. 

See subclause 5.5.1.2.5 of https://www.etsi.org/deliver/etsi_ts/124300_124399/124301/12.06.00_60/ts_124301v120600p.pdf.

A SIM replacement is not required. Simply re-insert the SIM or restart the phone somehow.

Colors in the image above were changed, because naming the network that sends "8" is not within the scope.

You may be affected if you are located in or near Accra or Tema, and are using one of these networks:

• MTN Ghana;

• Vodafone Ghana;

• Removed, because it was solved.

AirtelTigo and Glo might not issue USIMs (4G-capable SIMs), subject to change.

Until this issue is solved, you can prevent this issue from occuring by preventing the phone from using (removed, because it is solved):

• For MediaTek phones (used by multiple brands): dial *#*#3646633#*#*, then select BandMode. If this code doesn't work, there are many apps that may open MediaTek's engineer mode. Warning: May cause unintended operation.

• For newer Samsung phones, use this app: https://play.google.com/store/apps/details?id=com.ray.samsungbandselection. Settings are applied to the SIM chosen to be preferred for phone calls. Warning: May cause unintended operation.

• Set the phone to use 3G/2G, without 4G LTE.

• Use a 2G SIM, i.e. a SIM that's compatible with only 2G and 3G.

How to detect this issue:

Loss of signal with no reconnection afterwards, even after re-entering your network's coverage area. Unfortunately, this can be ambiguous, but can be narrowed down if the signal was trending down. There is no standard way to detect this issue without ambiguity on all mobile phones.

How to detect it (if it is possible to do so without ambiguity) ranges from simply dialing *#0011# for some Samsung phones ...

... to generating a .qmdl2 to be viewed with programs that can read it.