When creating or editing cards in Workstation, new features from each new Strategy 2019 Update (like templates, additional formatting options, and contextual linking) are disabled in the card editor. A black banner appears along the top of the editor saying “You are connecting to an older version of Library Server, some features may not work as expected."

Your Library Server may be an older version than your Workstation client. As such, new card editor features available in newer Workstation clients will not be supported on older versions of the Library Server. These features are disabled when Workstation is connected to an older Library Server.
Cards can still be created and edited in a limited capacity when the Workstation client is newer than the Library Server. To take full advantage of the newest features, it's recommended that you upgrade your Library Server to the same version as the Workstation client.
If your Library Server is the same version as your Workstation client, you may need to redeploy your .war file.