Hi Brian,
I’m in Minneapolis too and was just troubleshooting something similar yesterday. The main fix that I needed to make, along the lines of what Cal posted was increasing the timeout time in TinyGSM, which if I recall correctly was set at a minute. I increased it to 20 minutes to safely fall within the range of times that Cal posted. The Xbee3 consistently takes about 12 minutes to connect to the hologram network from my office (though I do have an antenna). I’ve seen on the Hologram forum that this could be due to both the NB-IoT and LTE-M being available to the modem on startup. As an aside, I plan on trying to send AT commands to specify LTE-M and AT&T to speed up connection times (it’s a drag to wait 20 minutes every time you troubleshoot).
I also observed the need to define the modem serial at 9600 baud like Cal did (confirmed in the Digi documentation that 9600 is the default for the Xbee3).
Since you aren’t seeing data usage on Hologram, I wonder if one of those points (connection timeout or serial setting) might be the problem.
Welcome to EnviroDIY, a community for do-it-yourself environmental science and monitoring. EnviroDIY is part of WikiWatershed, an initiative of Stroud Water Research Center designed to help people advance knowledge and stewardship of fresh water. 
