Hi,
I have the same problem with my new RS2.
I inserted my SIM Card (O2, APN: internet), tipped in my PIN code and see that there is a connection in the top left windowbar (but only one beam).
When i try to switch the Mobile Data On - it takes a moment and then stays off.
try to disable the pin on the card.
for this you could put the sim in a smartphone and then go to the settings and disable the pin for the simcard.
in my case that seemed to help.
only thing left is that sometimes after power on the sim is no detected at all…
as i partly helped the real owner of the device i currently don’t now how often this happens…