says it pretty much all there .
somewhere in your email settings (templates perhaps or email in your wppizza->order settings)
you have set an email of [email protected] that does not exist/is unroutable

you’ll have to speak to the mail administrator of that domain to fix that (or of course not send to that email in the first place)

depends on what exactly you want to accomplish.
the easiest though would be to simply add some css declarations
i.e something like
#wppizza-article-prices-xxx {display:none}
or even (better probably, but depends on exactly how your prices are set up)
#wppizza-article-sizes-xxx {display:none}

where the ‘xxx’ equals the id of the menu item.
(might also want to have a look at https://docs.wp-pizza.com/developers/?section=frontend-css-styles-layout )

if you truly want to not display them at all (i.e not even in the sourcecode of the page) you’ll have to get your hand s dirty with some wordpress/php coding/filtering
(if you need that and are happy to do some php coding, let me know and i’ll find some filter that allows you to do that)

>So It seems that for some reason that a id 0…
what happens if you duplicate the one with id 0 and subsequently delete the one with ID 0 ?
(there *might* be an empty() check somewhere – which would also return true if the id == 0 – that should be isset() instead ) ?

> retrieve the currently applied discount by its ID…
you could do something like this

add_action('init', 'myprefix_discountids_applied');
function myprefix_discountids_applied(){
	/***
	 session are per blog if multisite
	***/
	if(is_multisite()){
		global $blog_id;
		$session_key	= 'wppizza_cad_'.$blog_id;
	}else{
		$session_key	= 'wppizza_cad';
	}	
	
	$discount_ids = $_SESSION[$session_key]['discount'];
	
	/*
		now do something with the $discount_ids
	*/	
}

>if I could determine if there are more than one discounts at play…
the above will tell you if there’s one or more at play (as there will be none, one, or many id’s in that array)

>apply your own logic…
i suppose i could add a filter somewhere, however, if you want to apply your own logic you could also simply add your own discount(s) depending on your logic, using the wppizza_fltr_discount filter – which is essentially what the plugin does – along these lines

add_filter('wppizza_fltr_discount', 'myprefix_apply_discounts',10, 3);
function myprefix_apply_discounts($discountvalue, $session_items, $order_parameters){

/* alter the current discount value as required */

return $discountvalue;
}

Have you looked in your (javascript) console for errors ?
Have you enabled debug – https://docs.wp-pizza.com/troubleshooting/ – and checked your debug log ?

PS: what version of wppizza btw ?

> … Do you take over the project? ….
Sorry, I do not offer any customisations / custom coding ( https://docs.wp-pizza.com/faqs/?section=customisation )

> … Redsys is the way to integrate it …
There is a skeleton gateway in “/wppizza/add-ons/gateway-development/” you can use to develop your own gateway implementation depending on the API / documentation of the gateway you want to integrate

can you post a screenshot of your settings please

you can use the “elements” attribute in the shortcode to change the “order of appearance” of things
https://docs.wp-pizza.com/shortcodes/?section=by-category
i.e
[wppizza category=’vandaag’ noheader=’1′ elements=’title, thumbnail, content, prices’]

(or – as you are not using any thumbnails it seems – just ‘title, content, prices’ should also suffice I would think)

sure.
the idea is that if you buy 3 at a fixed price, you should also be able to buy 6 at 2x the fixed price
after all, i could just send you 2 separate orders – with more work for you – and i’ll get the discount 2 times regardless

NOT enabling MultiApply does not make too much sense to me in the first place to be honest (but it’s there if someone really wants it and there may well be circumstances/setups where this might be totally appropriate too)