Excel Solver Add-In

I am currently trying to enable solver for excel on my Macbook air, however, every time I try to enable it I get this message: 

Microsoft Excel cannot access the file '/Applications/Microsoft Excel.app/Contents/Resources/en.lproj/Add-Ins/Solver.xlam'. There are several possible reasons:

I have looked everywhere to find a solution to this but I can't figure it out, does anyone have any idea what the problem is and how to fix it?