I use Wolfram Programming Lab (Standard License). Normally from the Desktop version on an up-to-date Win10 PC. Last Thursday I updated to version 11.0.1 from 11.0.0. This worked with no problem.
I was developing a pretty large and tricky notebook (.nb) for two weeks. It was stored within the Wolfram cloud and is still there. I worked with it last Friday after the update and saved it to the cloud. No problem.
Since Saturday I cannot reopen that notebook. The ProgLab-Desktop says: "There was a syntax error in the file being read. Do you want to open it as plain text? ... If you are able to fix the error, save the file and open it again".
Let aside that my notebook had no syntax error when last saved on Friday evening, it's somewhat ridiculous that a program with a syntax error cannot be reopened.
When I answer YES to open the file as plain text, I get another error message: "There was a syntax error on line ... The error was: <lots of zeros>". Then the file opens empty as white space. No notebook, no plain text. Just one header line "Notebook[{},...".
When I try to open that notebook directly from the website (https://lab.wolframcloud.com/app/. Not the desktop version), it opens completely empty with no error message at all.
I'm afraid, I lost that program and have no idea, why. It is still in the cloud, 1MB large, saved last Friday evening, which is correct.
Does anyone have an idea how I could regain that notebook-file?