You do not have permission.

Which account did you use while trying to save the crossword? Did you add that account to the list of editors for the project?

I used my wpadmin account to (try to) create and save puzzle.
Under Assign projects and editors: wpadmin is Full project editor
Under Options>Roles: Admin, Editor and Author hvae Full editing rights.

First, what should happen is this:

• If you are logged in and you open the crossword creation page, saving the riddle should not include entering your username and password.
• If you are not logged in and you open the crossword creation page, the Save dialog should include username and password fields.

You might want to try both variants. Do not log in/log out while the page is open.

If this doesn’t lead you anywhere, setting the page into Debug mode might reveal more. The error message will then include a reason why you can’t save.

Please remember that using Debug mode on a site that can be publicly reached is a serious security hazard.

I just fixed a bug where multiple shortcodes in one page lead to the permission error you got. If that was the case for you (for example because you have the design and solving areas in the same post, or on a overview page there is more than one post with a game area), the new version 0.7.3 might help you out.