that's right @SultanRana ,
many times could happen there is just a mandatory field not filled up.
i.e. if you delete a manufacturer then try to edit a product that had that manufacturer, the button save won't work: you must scroll down to see the error in the "manufacturer" field.
that could be tricky because the user expects the error to appear on top of the page too, as usually happens with html5 forms.
anyway, hope that could help people troubleshoot the issue in the most simple way before trying to redeploy or edit the code
cheers!
