When we try to open the workflows in the SharePoint Designer, sometimes we receive the below error:
You can access the workflow from the SharePoint UI. Other workflows in different web applications are editable.
Cannot be same in all the scenarios but should be specific to the features
Capture a fiddler trace while opening the SharePoint designer and you should see a 505 error with the below error tag:
<errorstring xmlns="http://schemas.microsoft.com/sharepoint/soap/">Failed to find the XML file at location
This is due to the feature which is not available at '14\Template\Features'. If you have a custom solution whose web parts are placed in a web site and the solution files are missing or the solution is retracted, you see this error.
Remove the web parts that the solution adds to a site collection using PowerShell/code or deploy the solution back to the farm to get the feature.xml.
Read more about this:
Unable to load workflow actions from the server. Please contact your server administrator
SharePoint Designer 2010 - “Unable to load workflow actions from the server…”