Something went wrong. To try again, reload the page and then start the workflow, error on starting a workflow.

sharepoint designer workflow is howing above error message when tried to start worfklow manually on list item, and worflow is not triggered on item added or updaed event.

This was happening for only few lists. On other lists workflow is triggering with out any issue.

Reason for the issue: we modified the default display and edit forms of the list which are throwing issue. 

Removed the pages which are modified for customization and added new pages using designer making new pages as the default display and edit forms then designer workflow started working.