The transition seems correctly defined in your html page.
Please may you run your webApp in Preview mode in AC, with the Debug checkbox checked, and tell if it displays any errors message?
I wonder if it is the Storage activity that generates an error, but you should get an error 500 or something else. Otherwise you can look for an error in the AC web.log file of the public web server if you can acceed it.
In debug mode, please check the context shown in this part: