Term Store management option missing in Site Collection settings
When you don’t see the Term Store Management option in your site collection settings:
A hidden web application feature is probably not activated. You can activate it through PowerShell or stsadm:
Enable-SPFeature -id "73EF14B1-13A9-416b-A9B5-ECECA2B0604C" -Url <Site-URL>
stsadm -o activatefeature -id 73EF14B1-13A9-416b-A9B5-ECECA2B0604C -url http://<url> -force