Our MBR550 router comes with a USB flash drive that needs to be plugged into the router's left front (USB slot). The extra storage is required during Carrier Update processing. For ALL products, you need an ACTIVE INTERNET CONNECTION to something other than Cellular. That usually means WiFi unless you have another WAN/Internet source.
Our Routers have a page within Settings > Miscellaneous – found near the bottom under “Advanced Settings”. There is a hyperlink (a weblink) “click here” that accesses that.
This first presents the WiFi AP country and power settings, and below that section, it will start by “Checking for installed mobile data interfaces”. Then it will show a list of installed carrier firmware(s). There is a paragraph about that with a “Click here” link to check for available carrier updates. Click that link.
After that, it will come back with a line in GREEN telling you of success and presenting an updated list. If you get Radio Buttons (checkboxes) between installed and needed carrier firmware(s), you need to update. You do not have to update carrier drivers that you do not use. Most are named by the carrier. T-Mobile uses GENERIC. Some other carriers that do not have specifically named firmware updates may also use GENERIC.
From there, you are checking the boxes you need and click the “Update” button at the bottom of that section.