Build failed and i dont know how to fix this

[SteveJG]

The recommendation is not to use more than 10 Screens. Sometimes more can be used and then the developer has issues.

Are App Inventor Projects Limited to 10 Screens?

There isn't a hard limit on the number of Screens in an app. When used properly, multiple screens are a perfectly reasonable way to organize your app. For example, in a app for finding restaurants you may have a main screen with a map, a second screen that shows restaurant data, a third that shows menu contents, a forth that shows pictures of food, a fifth that shows reviews, etc. In this design each screen is a view over some model (cf. model-view-controller design pattern). The wrong way to u…

My guess is you get the error because of how you use your Screens or in your case number is a factor. Make a copy of your Project; remove a screen and try to recompile. Then do it all again until your projects run might find the problem.