@QueenofHearts-
Does your Ultra have an SD memory card installed? A corrupted card can have the effect you described. Removing the SD card may allow your Roku to complete its login.
Try formatting the card in your computer, if it has a card reader that can handle SD cards. After formatting, see if the Roku will detect and reformat the card successfully.
Also, see if this post helps: https://community.roku.com/t5/Remotes-Accessories/Added-SD-Card-Remote-no-longer-works/m-p/646676#M1...
Windows instructions, don't know what would differ on other systems: Do a slow (i.e. not "fast") format of the card via your computer. Select FAT32 and select it to use the default allocation size.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X