When user click on an attachment in the form on form site it shows an error "The Hostname in the redirected URL is invalid"
Alternate Access Management(AAM) configuration in the SharePoint environment.
1. Open Workflow Administration site.
2. Check for key "AllowedHostnames" configured or not.
3. If not, Add key "AllowedHostnames" with value "hostname of the server where workflow is installed" eg.: "USMKASRVSPW301"
4. Do the IISREST
5. Re-run the use case.