I've recently swapped to the new purple SIM. Unfortunately, my phone keeps saying No SIM. After starting up it might work for a few minutes or a few hours but then the SIM 'disappears' and the phone reports No SIM. If it 'reappears' the phone reboots. I never had any trouble like this with the old SIM.
Could my phone me incompatible with the new SIM? I have a Sony Xperia M5
Could the SIM be ever-so-slightly thinner and so not making reliable connection in the slot?