Hello Erel, i bought a new version of B4A. With the last version when i dowloaded my programs , i had no problem. With the new version, if i recompile my old programs and i want dowload them on my smartphones i have a message which said to me that the program can't be installed on the smartphone. So I can't understand.
Have you tried to uninstall the old app from the device? The debug key was changed at some point. If you were using it then you need to first uninstall the old app.
As a test you can change the package name to a new name and see whether it works.