Visual Studio Xamarin Android App Build Fail

I am working on a Xamarin Android App with visual studio community 2015, after working for a while, I compiled it in release mode to generate .apk, I signed it and installed it on a device. I opened mthe project to continue building and noticed that it did not build. and it still hasn't built. I have restored nugget packages, deleted bin and obj files etc. none seem to work. Here's the error

The "InstallPackageAssemblies" task failed unexpectedly.
2>System.AggregateException: One or more errors occurred. ---> Xamarin.AndroidTools.AndroidDeploymentException: InternalError ---> Mono.AndroidTools.InstallFailedException: Failure [INSTALL_FAILED_UPDATE_INCOMPATIBLE]
2>   at Mono.AndroidTools.Internal.AdbOutputParsing.CheckInstallSuccess(String output, String packageName)
2>   at Mono.AndroidTools.AndroidDevice.<InstallPackage>c__AnonStoreyF.<>m__0(Task`1 t)
2>   at System.Threading.Tasks.ContinuationTaskFromResultTask`1.InnerInvoke()
2>   at System.Threading.Tasks.Task.Execute()
2>   --- End of inner exception stack trace ---
2>   at Xamarin.AndroidTools.AndroidDeploySession.<RunLoggedAsync>c__async1.MoveNext()
2>--- End of stack trace from previous location where exception was thrown ---
2>   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
2>   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
2>   at Xamarin.AndroidTools.AndroidDeploySession.<StartAsync>c__async0.MoveNext()
2>   --- End of inner exception stack trace ---
2>   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
2>   at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
2>   at System.Threading.Tasks.Task.Wait()
2>   at Xamarin.Android.Tasks.InstallPackageAssemblies.Execute()
2>   at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
2>   at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__26.MoveNext()
2>---> (Inner Exception #0) Xamarin.AndroidTools.AndroidDeploymentException: InternalError ---> Mono.AndroidTools.InstallFailedException: Failure [INSTALL_FAILED_UPDATE_INCOMPATIBLE]
2>   at Mono.AndroidTools.Internal.AdbOutputParsing.CheckInstallSuccess(String output, String packageName)
2>   at Mono.AndroidTools.AndroidDevice.<InstallPackage>c__AnonStoreyF.<>m__0(Task`1 t)
2>   at System.Threading.Tasks.ContinuationTaskFromResultTask`1.InnerInvoke()
2>   at System.Threading.Tasks.Task.Execute()
2>   --- End of inner exception stack trace ---
2>   at Xamarin.AndroidTools.AndroidDeploySession.<RunLoggedAsync>c__async1.MoveNext()
2>--- End of stack trace from previous location where exception was thrown ---
2>   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
2>   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
2>   at Xamarin.AndroidTools.AndroidDeploySession.<StartAsync>c__async0.MoveNext()<---
2>
2>Done executing task "InstallPackageAssemblies" -- FAILED.
2>Done building target "_Upload" in project "appiness.csproj" -- FAILED.
2>Done building project "appiness.csproj" -- FAILED.
2>Build FAILED.
2>