Apk update issue

hi guys, i have same project configured in two systems, one in lap and another in desktop.with same configurations.the project version and package name are same . when i take production build in laptop and install on the phone it works as usual. if i take the build from desktop(pc) for the same project, production build and installing on the phone. it asks “do yo want to install an update to the existing application ?” if i click install, it says “App Not Installed” . any ideas?? . how to fix this. i don’t want to lose the existing apk. i need an update. it is just production build. i don’t want to lose the old data. any ideas.