Why does Blurb Bookify's startup progress bar freeze at 99%?

Question

I have a couple of users interested in using Blurb's "Bookify" flash app for creating photobooks (although that link may redirect to the download for the desktop native app if Flash isn't installed).

Both users have logins on a (high-end) machine running Linux (Debian "Stretch" 64bit) with Firefox (ESR) 52.4.0 and Adobe Flash 27.0.

For one user, the "Bookify" application appears to run absolutely fine.

For the other user (on the same machine, using the same browser and flash version!), it shows its startup progress bar dialog... but that bar freezes at the 99% point forever.

I've tried clearing all "blurb" cookies, clearing browser cache... but nothing seems to improve situation for that user. Whereas the other user continues to have no problems when they attempt to use the app.

Any ideas how to "unstick" it?

Someone posted the same/similar problem on Blurb's FB page a while ago; no solution posted there but I'll try messaging them myself. (There's also another mention from around the same time here).

Answer 1

This issue was resolved: with Firefox closed, the user with the problem ran the flash-player-properties tool and on its "Local storage settings" tab used the "Delete All" dialog's "Delete All Site Data And Settings".

Then when Firefox was restarted and the Bookify page visited, the progress bar completed and the application appeared as expected.

It seems the user experiencing the problem had used Bookify at some point in the past. I'm guessing that at some point the application was changed in a way that it was broken by old versions' local saved data; that'd explain the multiple users apparently experiencing similar difficulties a few months ago.