I'm not the original guy asking for help but I have the same problem. I tried to sideload it with ADB but it didn't work and came up with this error message 'failed to install LD+E.apk: Failure [INSTALL_FAILED_UPDATE_INCOMPATIBLE: Package indivi.indivigames.lustdollplus signatures do not match previously installed version; ignoring!]'. so from my understanding its best to just backup lust doll using what you say in your other comment delete the game and restore the data to lust doll essentials.