I am having trouble with my form validation. Each of the fields is required and should be highlighted accompanied by an error message if left blank or if only a space is input.

This works only once after the page loads, if a field is corrected and the form is resubmitted the fields should be revalidated according to the ammended inputs, but this doesn't happen. The submit seems to remain disabled. but I am not certain this is what is happening.

You can see the form here.

Can anyone help or advise me? I am at a loss...

Thanks in advance.