Itunes wont recognize my library file on my external HD

I recently moved my iTunes library to an external HD. Everything worked fine by hitting opt/alt iTunes and selecting the library file on my external HD. When I reformatted my MacBook Pro to Yosemite 10.10.2, I can no longer select the library file--it is greyed out within the iTunes folder. I know that it all should work and have read countless threads, but none seem to help. Is there something I need to do in order for iTunes to recognize the Library file?

Thanks!