i’m working on a project for a friend and after some revision ( a make a new copy of the project after few code implementation), i lost the ability to change screen size in the APP inventor IDE.
Now i cannot switch screen from phone to tablet, but i’m not shure is something i set in the code or an app inventor bug.
someone has a suggestion or an hint?
Change the screen1 property SIZING to “Responsive”.
you saved my day 
This is something that doesn’t get saved with the copy. When you open a copy of a project, sizing is reset to its default.
May be it should be changed in future releases?
Hi @Italo,
This is news to me. We do have upgraders that run on a project that should appropriately save the corresponding state when loading an older project. Can you show us an example where it’s not working correctly?
Sorry, this was the case when FIXED was the default. Now I see the default is RESPONSIVE. I just made a copy of a responsive project and it did it right. So no problems there. False alarm! 
Then I don’t know what happened with @allegfede’s project. May be they changed the sizing inadvertently.
I can imagine is caused by switching the project from App Inventor to AppyBuilder and back (i need the “screen copy” feature of AppyBuilder)
You are fortunate you did not bring back an incompatible component from AppyBuilder in your project file. Decontamination facilities among AI2 distros do not exist.
Probably that's what caused it.