Hi,
This code seems to be missing from your view "checkout / login":
$js = "window.hikashop.ready( function(){displayRegistration(window.document.getElementById('data_register_registration_method".$defaultSelection."'));});";
$doc = JFactory::getDocument();
$doc->addScriptDeclaration("\n<!--\n".$js."\n//-->\n");
Please add it just before:
echo JHTML::_('hikaselect.radiolist', $values, 'data[register][registration_method]', ' onchange="displayRegistration(this)"', 'value', 'text', $defaultSelection, false, false, true );
If the code is already present, please change the value from switcher to all in one page, save and change it back to switcher in Configuration > Checkout > Login & Registration.