Why Loop cut not cutting completed Image 1


Image2


When I do Loop Cut as in image 1, its not coming like image 2.. what can be problem , I have removed doubles , manifold geomertry, etc. nothing works fine for me..

I have uploaded the blend file here - https://filebin.net/n3mrxwjbsvcs02ck/GoodDinasoure.blend?t=wuah6hdx

Please help i am following some tutorial and struck here.. otherwise i will not able to complete.. thanks
You have a ngon but you don't see it because you have 2 of its vertices overlapping, so remove one of those, or select all and remove doubles with enough Merge Distance (0.02).