If you can’t find ‘Term Store Management’ under the Site Administration section in Site Settings, there’s a very simple PowerShell fix for this due to the fact that a feature has not been enabled on the box.

Just enter the following PowerShell command (Run as Administrator):

Enable-SPFeature -id “73EF14B1-13A9-416b-A9B5-ECECA2B0604C” 
     -Url <yoursitename>