Disk cant open after using file sharing

I was testing the read and write speeds of my hard drive over wifi to see if it was suitable for a backup. After plugging it into my computer, it now gives the error "The Folder "Hard drive Name" can't be opened because you don't have permission to see its contents. It wasn't like that before I plugged it into my airport extreme. How can I fix this?

There was a password protecting the drive while it was in the airport extreme.

Thanks