I suggest you cut down the questions here, I think too many to answer all at once. First I’d focus on getting registered, has the device ever registered “worked” with the Hologram simcard?
Either way, when it doesnt work run the commands: https://help.hologram.io/en/articles/1944384-modem-sim-annotated-diagnostic-test and post the results, that should help identify exactly where things are going wrong.
If there is an ATT starter kit forum or other user forum around that kit I would suggest posting there as well especially about your GPS issue.