When you move K2 to a new server with a different hostname, previously running workflows will show a message that they cannot find the hostname of the previous server.
Usually this will occur after upgrading to K2 Five. Since the minimum requirements for infrastructure has changed for K2 Five, you would usually upgrade your infrastructure at the same time as upgrading your K2 version. Usually that entails installing K2 on a server with a different hostname, which will lead to workflows that were in Running or Active state to run into an Error state.
Process Instances in K2 Workspace / K2 Management will end up with an error that looks like this:
"1 Unable to connect to HOSTNAME on port 5252. A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond."
The most important thing is to check and confirm that your Environment Library entries are all pointing to the correct locations. For example, the Connection String building up the "Workflow Server" entry should point to the correct K2 server hostname.
After you are certain that all newly started instances of a workflow will use the new K2 Server's hostname, then you can proceed to modify the HOSTS file.
Please open Notepad as Administrator, then browse to the following location and open this file:
Add this entry at the bottom of the file:
Please replace "OLDHOSTNAME" with the hostname of the previous K2 Server and save the file, then restart the K2 Service.
All your previously running workflow instances should now be working again when you click on the "Retry" button.