Unable to connect

I upgraded my macbook pro to mavericks and I am unable to connect to my MacBook live.  What can I do so that time machine will connect with the external hard drive.  I keep getting the following message:

“no mountable file systems”

Hello and welcome to the WD community,

Make sure you can see the unit on finder and try to access it, this is a good first step to make sure the unit is accessible through the network.