Hi Joyce,
I'm sorry you are running into this issue. Can you please try the following to see if the issue can be resolved?
1.Quit Google Web Designer.
2. Delete the cache folder:
Windows:
\Users\<username> \AppData\Local\Google\Google Web Designer\data\cache
MAC:
/Users/<username>/Library/Application Support/Google Web Designer/data/cache
3. Launch Google Web Designer again.
Please let us know if this resolves the issue.
San
Google Web Designer team