OK. You never mentioned what the updates were that started all of this, but evidently it wasn't firmware. If it had been, there would have been some trace of it being downloaded.
Ok, with the contents that I backed up yesterday, the behavior is exactly the same - yellow background with an ejected SD card with a red X.
I have another SD card that I formatted and restored backup made a few years ago - this time Home tool enabled me to link the device to the account I have at TomTom. Through the Home tool, I went to update my device, it downloaded a few items including the QuickGPSFix and application and applied everything successfully on the card. I ejected the card and put it in GPS Device - no dice - I get the same yellow background asking me to take out the SD card with a red X. Now it doesn't recognize the SD card and doesn't allow me to Link my device in Home tool.
I need to reformat the SD card and repeat the process - I need to see if I can get the GPS working at the stage it was last week before the update.