AT&T aircard on Windows10

I am having a lot of trouble with AT&T Aircard model 313U (made by Sierra Wireless) on windows10. This device works fine on Windows 8. It also seemed to work ok with Windows10 RTM. Any non-RTM versions like the preview versions, it won't work. It immediately disconnects from the network without any errors. I've tried the AT&T software. I've tried Aircard watcher from Sierra Wireless. Nothing. I tried using a mobile broadband connection directly thru Windows10, and that disconnects with the error "Can't connect to this network. Enter an APN and try again".  The profile in Windows 10 has an APN of "broadband".  I've tried a million other APNs that i have found on various forums, to no avail.  Any ideas?