0000021015 [ncp.at] TRACE: > AT+CEREG?
0000021016 [ncp.at] TRACE: < +CEREG: 2
0000021064 [ncp.at] TRACE: < +CEREG: 2,2
0000021065 [ncp.at] TRACE: < OK
0000036065 [ncp.at] TRACE: > AT+CEREG?
0000036114 [ncp.at] TRACE: < +CEREG: 2,2
0000036115 [ncp.at] TRACE: < OK
0000051115 [ncp.at] TRACE: > AT+CEREG?
0000051164 [ncp.at] TRACE: < +CEREG: 2,2
0000051165 [ncp.at] TRACE: < OK
That sequence indicates that no cell tower is accepting a connection from your Boron. Unfortunately the Boron LTE modem (u-blox SARA-R410M-02-B) doesn't allow a carrier scan like the 2G/3G modems do, it it's really hard to determine whether it's no towers, no compatible towers, or what.
There is a possibility that LTE carrier auto-detection is not working with your AT&T SIM. You might need to set it explicitly like you do with Hologram SIMs on LTE. It's explained in this post, just use mnoProf = 2 for AT&T instead of the Verizon setting used for Hologram.