These things can happen for multiple reasons. You might already have an app with the same package name installed on the device with a different signature. That can cause problems.
If you look through the logcat/ddms log of the device you should see a more detailed error message when you try the install. -- You received this message because you are subscribed to the Google Groups "CodenameOne Discussions" group. To unsubscribe from this group and stop receiving emails from it, send an email to codenameone-discussions+unsubscr...@googlegroups.com. Visit this group at https://groups.google.com/group/codenameone-discussions. To view this discussion on the web visit https://groups.google.com/d/msgid/codenameone-discussions/820de99e-b901-4b27-b18e-8a99ca94e079%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
