The BandLab Assistant update failed for me too after it tried to update automatically. Same symptoms as others: "Authorization Error" and BandLab Assistant hangs. I followed suggestions from the above posts and it works now.
Here are the steps I did (based on the input from previous posters):
1.) Terminated multiple "BandLab Assistant.exe" processes (via task manager).
2.) Uninstalled the existing BandLab Assistant (wonder if this is necessary).
3.) Downloaded and installed the latest BandLab Assistant from here:
https://www.bandlab.com/download/assistant/windows https://www.bandlab.com/products/cakewalk/whats-new <- Try this path if the above doesn't work.
Thanks to the folks who posted above with the various suggestions.