I have had similar problems being able to connect to any network when using my FP2 in East Africa. I am UK based and have been able to connect to other networks when roaming in Europe, but not across Kenya, Tanzania and Uganda, whether in cities or rural areas across the three countries. The one exception, oddly, is that I can connect to a network in the capital of Uganda and in DR Congo.
I try manually selecting networks in East Africa and several different networks are available (all the usual for those countries - Safaricom, Airtel, Orange, Tigo, Vodacom, MTN) but every time I select any of them, it says ‘Cannot register on network.’
I have tried ordering a new sim card in my FP2 but that didn’t work. My home network provider assures me they have not blocked data roaming but also suggest I need to text from the phone in East Africa to got any roaming bans lifted, and of course I cannot text from East Africa as can’t connect to a network.
I have also tried using a local sim card in my FP2 and occasionally that will work, suggesting it is a sim issue. But on the other hand, sometimes a local sim will not work in my FP2 even though it will work in an old nokia phone I travel with, suggesting it is the FP2 not the sim.
I have tried all the tricks above like toggling flight mode one/off and rebooting. I have pretty much given up trying now and rely on wifi or an old nokia with local sim for emergency calls, but travel to E Africa a lot and there often isn’t wifi, so it would be very helpful to have roaming data and indeed any network connection at all with the FP2.