Server-side activities have been updated. You need to restart SharePoint Designer to use the updated version of activities.

When working with SharePoint Designer 2013/2016, you may get the following error:

“Server-side activities have been updated. You need to restart SharePoint Designer to use the updated version of activities.”

This issue can happen if Visual Studio and SharePoint Designer are installed on the same machine which is the case for development machines.

• Try installing SharePoint Designer update from https://support.microsoft.com/en-us/kb/3114337.
• Removing Visual Studio and installing it again should fix the issue.
• Check if you have Workflow Manager Client installed and uninstall it and it should fix the issue.