I have installed my 3G/4G/LTE hat, and sixfab core on a new raspberrian sd card per your instructions. The device gets an IP address for wwan0, but is not able to ping sixfab.com.
ifconfig wwan0 shows the following:
wwan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.225.59 netmask 255.255.255.0 broadcast 192.168.225.255
inet6 fe80::7ee8:f99a:97b6:21d prefixlen 64 scopeid 0x20
ether d6:2b:df:01:0e:68 txqueuelen 1000 (Ethernet)
RX packets 20 bytes 1429 (1.3 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 45 bytes 4601 (4.4 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
This hat and SD card worked with this raspberry pi before I did this new installation.