I have a Z3c got the Sim from AT&T after the unit was online I was able to see cellular was active. I unplugged my network and the unit worked great. Powered off the unit and restarted with no Ethernet connected and it will not connect to the Cell network. When it powers on does it always have to be on a wired network ? Also I was told to add "broadband" to my apn field did anyone else do that ?
Seen these with local carriers with my MX67C and customer Z3Cs here in the Nordics. After updating my FW back in January I managed to get rid off this problem with my MX67C. Before that appliance needed to be booted up with a wired connection. Comments from the field suggest that FW updates have fixed these issues for most of customers too.
What I find I had to do with the Z3c is I left it connected to a wired internet connection for a few hours. After all the updates and adding "broadband" it has worked great.