Ridiculous Cellspot setup issues

T-mobile has sent me 3 cell-spots because they can't seem to get their act together to get it setup properly. I work in IT network security, so I am familiar with firewalls and ports/protocols. I've got my cellspot connected to my ATT router, there are no packet filters enabled on the ISP's router. The cellspot is having issues registering with T-mobile. I've spoken to countless number of techs (including advanced). They solution thus far seems to be to keep swapping out cellspot devices. This has been on-going for over a month or so, it's ridiculous. Keep getting told to wait 72+ hours for the device to register, nothing ever happens. Latest call, tech submitted (again) a ticket and said to wait a few days and will follow up with me. I feel as if they are dealing with a cumbersome piece of technology and that their techs have no clear and defined process to fix the issue. Will see if this latest round of troubleshooting helps, but at this point I'm not holding my breath.