I remember talking to someone else who had that problem.
Are you using minlogon, by any chance? If so, did you install StreeDeck while using minlogon?
How do you make it where SDU or SDZ file extension get recongnize by SD again. Only way those files are read is if streetdeck is up and i stick in a usb drive. Beside that if i dl it and try to update it wont do anything. I try to change the program that it want to open to but it keep on picking IE.
.sdu files should be mapped to SDUpdate.exe, .sdz files should be mapped to StreetDeck.exe. This should be done by the installer automatically. If not, in windows, just right click on the file, choose Open With, then browse to the proper exe for the file format.