I'm not sure what to do with this... I had already downloaded the original 5.1 and created a new save file, so I have 2 apps labelled lust doll plus on my phone. When I download the reupload it says app not installed... The "original" lust doll plus (from 4.2) is still very laggy, while the original 5.1 is still the original 5.1...am I doing something wrong? Should I uninstall one of them?
Don't uninstall the laggy one. It uses the proper package name, so this version will be updated in the future. Try redownloading the app, and/or clearing some space on your phone. It's unfortunately a really unhelpful error msg. Can also see if something here works: https://www.google.com/search?q=app+not+installed+error&rlz=1C1CHBF_enCA862CA862&oq=app+not+installed+error&aqs=chrome..69i57.3247j0j0&sourceid=chrome&ie=UTF-8