Not showing validation message for required field.

I used the plugin for signature in one my forms, made that signature field mandatory. when clicking on submit button without signature, it is showing an orange bordered box without any information in it as by default it show as ‘One or more fields have error. Please check and try again’, but it is not showing. Also it should show red cross mark over the signature filed when it is not filled, even that is not working.

Kindly help with the above issues.

The page I need help with: [log in to see the link]