Powershell error : $NavIde was not correctly set.

Has anyone came a cross this "$NavIde was not correctly set." error when when executing any functions on NavModelTools.ps1 through powershell ISE ? I think I missed a step or two but I don't know what that step is. When running the same function using the "Microsoft Dynamics NAV 2015 Development Shell" shortcut I did not get this error.

I would appreciate if someone can help me with this.

Carlos