When the workflow task lists is opened in the Web Client, using the Internet Explorer, the following message occurs in the DocuWare web Client:

"Restart the Workflow Engine server and try again."

Check whether the website of the DocuWare Web Client, is in the security zone "local intranet". If the website is not in this security zone it should be added. Afterwards it
should be possible to open the workflow task lists in the Internet Explorer.

If the behavior does sill occur, check if the port 8117 is open on the DocuWare Server and all the clients. The port can also be accessed through the browser using the URL
http://[DOCUWARESERVERNAME]:8117, please open this URL to check if it is accessable.
In addition, you could try to open the workflow task lists using the Firefox.