The uconnect website is a joke, the update page on it doesn't actually work, I think they just leave it up so people think they have a little control over the product they paid for. You either have to pray you get an OTA update, OR go to your dealer and tell them your radio is acting up, and the dealer should have access to firmware updates and should be able to upload one for you... If they give you a hard time you can see if you qualify for this recall:
https://www.consumerreports.org/car...ep-ram-recall-rearview-backup-camera-display/ which should bring you up to the latest firmware release.
In my 12" Uconnect I had firmware 18.45.40, with a build date of november 2018, and this firmware was too old and did not support the TTPMS features. Since i added my 12" Uconnect after i bought the truck local dealers were giving me a hard time about updating the firmware, but I was able to squeeze one of them by referencing the Recall, and that brought me up to firmware
19.43.1a or newer, and that unlocked the Trailer TPMS menus in my Uconnect.
Edit: just checked the recall update brought my radio to 20.04.19 with a build date of January 2020