Hi: Like you, I've been waiting for a true fix to the problem giving us the error code as well. However, try this as a temporary work-around until Microsoft and/or Kindle fixes the original problem.
Make sure that you have a second email address listed in your Kindle.
Go to your OneDrive cloud account on a PC that will let you access OneDriveand click your notebook and then Share. It will ask for a email to share your notebook with. Name the second email that's in Kindle.
Open Kindle and look at your email. There should be one titled "I shared "X's Notbook *** with you in OneDrive. Hit the View in OneDrive and see if your notebook opens in Silk.
Not great, I'll admit but until it gets fixed, it's better then nothing.
Hope this helps
I think I'll have a shirt made with "There's a problem - We can't complete this task. Try again.
Error code: 80004005" on it.