If you are trying to add SmartCite, but your Add-in button is grayed out, this means your IT department has to Allow SmartCite because your organization is on a Microsoft Enterprise license.
Not to worry - it's an easy for your IT team to add and if they need additional information to do that, please contact us at ReadCube Papers Support.
In a nutshell, through the admin panel, your administrator can assign an add-in directly to a user, to multiple users via a group, or to everyone in the tenant. When the relevant Office application starts, the add-in automatically downloads for set of users your IT has permitted.
You can find step-by-step instructions here:
Manage deployment of Office 365 add-ins in the Microsoft 365 admin center
Once added, you will be able to find SmartCite either already pushed to your ribbon menu bar or if not, under "Admin Managed" tab in your Add-in menu.