Media offline and trying to relink but the External HD is not showing up

Hi ya'll! I'm having trouble relinking to my files. I deleted all of media cache earlier because my Project file keep freezing up and after I deleted the media cache, everyting was offline. When I try to relink the file my hard drive where has all the file is not showing up at Local Drives catagroty, I can see my hard drive but it won't let me open it. Can anybody help me with this???