External HDD not being read anymore?

I have a 1.5tb drive that connects via usb. Worked for years.

Now my air wont read it.
My TV will so I can watch all the files there but why wont my mac air read it now? =(

I have tried everything I can think of, restarts, new cords, etc.

Does anyone have any ideas?

Nope, tried that.

I go into disk utility and I can see it, but it's greyed out and "unmounted" I clicked repair but it says it cannot repair.

Any other tips?