Workflow page throwing error

Hello,

I have configured the workflow manager for SP 2013 and also published a workflow..The issue is if I leave the workflow to automatically start it startes and finishes correctly..When I change it to manually start and I go to start the workflow the page throws an error..I checked the logs and it's throwing a 500 error when I try to access the _layouts/15/workflow.aspx page..Any idea what might be going on here.

Thanks