Xamarin Forms has an intermittent bug where an app will build and successfully deploy, but when checking the app of the device/emulator, the app hasn't updated at all and remains running an old version of the app. The solution to this lies within the bin folder of your project.
The problem seem to happen regardless of the version of Visual Studio or Xamarin and hits a single project specifically so this tells us that the issue has altered something within the project and not within the Visual Studio installation.
Before you begin, uninstall all versions of the apps from all emulators and devices you use to test the app, this will ensure that once we've corrected the issue, it'll be able to fresh install instead of update.
Once uninstalled, navigate to the solution folder on your disk drive and open the folder of the project that this issue effects, you'll need to delete both the Debug and Release folders from both the bin and obj folders. You should now be able to deploy the project to a device or emulator without issue and it should be the latest version.
See the following thread on the Xamarin forums for more info:
By Luke Alderton at 25 Jul 2017, 12:01 PM
Tags: Xamarin,Xamarin Forms,Android,C#,Visual Studio