Uploading App Problem

I get this error message:

The versionCode from AndroidManifest.xml is missing or is invalid. Your application must have a valid version code (versionCode) field. You need to edit your AndroidManifest.xml file to fix this, and then upload again the .apk file.

I made the app with Google App Inventor, so is that the problem?

You can get more information

You can get more information here: Versioning Your Applications

Regarding the application uploading problem

I got your problem, You need to change your versionCode because you have already published the application and you are going to publish the new version of the same application so you need to change the versionCode and versionName, versionName is only use to show the version Name to the user and version code is used to check the previous version of your application. If you publish new app with the same versionCode you got the error which you have posted so Change your versionCode and versionName in application menifest file.