Microsoft.Lightswitch.Build.Tasks.Targets(168,5): application definition contains critical errors

I have a complex lightswitch application that was created using visual studio 2013, and then I upgrade it to using visual studio 2015. the solution was working fine, I even did a couple of deployment for it. Now I am trying to build it from a new machine and the build hangs (it never finishes). The output console is displaying an error: Microsoft.Lightswitch.Build.Tasks.Targets(168,5): application definition contains critical errors

I tried Google for a solution but could not find one that works in my case, I already checked the Link1 and this one Link2

When I cancel the build another similar error is displayed this is the output console:

------ Build started: Project: Agency Tool.Server, Configuration: Debug Any CPU ------ C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v14.0\LightSwitch\v5.0\Microsoft.LightSwitch.Build.Tasks.targets(168,5): error : Application definition contains critical errors. ------ Build started: Project: Agency Tool.DesktopClient, Configuration: Debug Any CPU ------ C:\Program Files (x86)\MSBuild\Microsoft\VisualStudio\v14.0\LightSwitch\v5.0\Microsoft.LightSwitch.Build.Tasks.targets(217,5): error : Application definition contains critical errors. ------ Build started: Project: Agency Tool, Configuration: Debug Any CPU ------ The data necessary to complete this operation is not yet available. (Exception from HRESULT: 0x8000000A) ========== Build: 0 succeeded, 3 failed, 0 up-to-date, 0 skipped ==========

Resolved: We noticed that in the main project properties--> extensions tab, Microsoft Lightswitch Extensions was not selected (I don't know what caused it to be unchecked, but I did not do it manually). However when we checked it the error disappeared.