I am unable to add a new standard Channel as the 'New' button is grayed out.
All Versions / Standard Channels
The standard product functionality does not allow the option to add or delete the standard channels in reference to which incidents are created and responded to. There is not a workaround available for this. However, you are able to edit a channel name that suits your business requirements.
You are also able to edit channel types so that your agents can add information about channel user names by adding the Channel Usernames field to a custom contact workspace and then assign that workspace to the profile used by agents.
For additional information regarding channel categories and types, please see the Social Experience > Channels section in Documentation for Oracle Service Cloud.