Well, problem solved for your purposes Sjoerd but we need you to tell us step-by-step exactly how the project that fails was built, including changing accounts, to be sure we know how it went 'wonky'.
What I don't understand is, how the issue only affects you and not any one else that imports your project - if the paths issue is corrected when a project is imported, why did that not work with your new account?
Another concern is that teams working on the same project often pass the same project file to other team members to do their bit. Also Power Users often modify projects for stranded Users, yet this issue either does not occur or the APK somehow survives it.
So in conclusion, we need to find a way to either prevent this happening, correct it on the Desktop (not ideal) or have a checker-corrector in the App Inventor IDE.
I have made a project on AI in 2017. It was a project where I could control a relay board with 12 relays connected to an Arduino with a HC06 BlueTooth shield. I never got that working properly so I stopped. I did upload it to my phone then, just to see how that worked and I had no problems then. I could open the app on my phone.
Two weeks ago I decided to give it another try. I logged in on AI with my google account. The project from 4 years ago was still available in My Projects. I opened it, made quite a lot of changes. I deleted buttons and blocks, added new buttons, a switch and blocks. Tried a few other things like a slider and a textbox. Deleted these and so on. I was just experimenting while connected to the AI companion on my phone. I got it working this time so I wanted to install it on my phone and then the problem began.
Between 2017 and now I did not change my Google account, I only changed the e-mail address I use to log in to that account from sjoerd@van-staveren.net to sjoerd1953nl@gmail.com. In the screenshot @Boban showed us you can see that the parts before the @ in those addresses match the parts that he highlighted (ai_sjoerd1953nl and ai_sjoerd).
So somebody at MIT changed your login for you. This will be the point where the potential of a paths issue is introduced. I think it is possible that MIT could run a bespoke util to change the paths at the time the account ID is changed.
I am not sure who to give the credits for the solution. I looks more as a team effort to me:
@Boban was the first to see that there was an issue with two names and @Anke posed the right question wen she asked if the login was changed. Patryk_F and ewpatton suggested to use the code.appinventor. It was dora_paz who was the first to give me a working version of my app. ChrisWard gave me a helpful link for this and future projects (and they will come - I love this development tool) and fianly he wrapped the whole thing up.
So ladies and gentlemen, which answer should I select as the Solution?
P.S.
I mentioned you all in my post but then I got the message that I am only allowed two mentions in a post (new user).
