Doh!
I read this article [Support Guide] Form problems, form debugging, 404 when submitting and How to Integrate Netlify’s Form Handling in a React App and it got me thinking if the form-name
had to be the same value as the <form id=...
Apparently so, now it works again
Code change
<form id="OKConsultingContactForm" action="#" method="post" netlify onSubmit={handleSubmit}>
<input type="hidden" name="form-name" value="OKConsultingContactForm" />