Why can't see my Harddrive on my MacBook Pro?

So tonight I experimented with plugging in my Hard drive into my new wireless router which is made by NetGear and discovered that I can see my files wirelessly from Mac now which is great, but unfortunately I discovered that would I plug my Hard Drive back into my Mac it doesn't show up so please help me.

It's likely formatted as NTFS. The router can see it and so can you because at that point is basically a NAS and not an external HDD.

Thankfully after running scan for my hard drive with its software on my Mac I was able to see it again.