>2 per row
that’s not strictly true.
by default, it shows 3 per row and for small screen devices – up to 400px – 2 per row
it will always depend on your ingredients (i.e the names and name lengths) whether this is adequate for your particular scenario. if it is not (as seems to be the case in your situation) you probably want to add some more css / media query for smaller things. example (for up to 250 lets say, one per row)

@media screen and (max-width: 250px){ 
.wppizza-ingredients ul>li{width:99% !important;}
}

or similar

see also https://www.wp-pizza.com/topic/customising-the-add-ingredients-css/

>and I didn’t change a thing!
i most certainly did not either …..

>and then an answer like the one above

you did not ask a question …..

if it worked “in the morning” and then did not work anymore (and the plugin has – clearly – not changed ) then how could it possibly be the plugins fault or problem

moreover, i gave you a quite detailed css declaration (and a link to how to customise the css)

i have no idea what more it is you are expecting (not even mentioning I can only guess anyway as you did not even supply a link to start off with …)

ok, no worries.
am in the middle of something, but give me an hour or so and i’ll see what i can find.
will get back to you here

my *guess* is you added/created that custom css in the morning and subsequently updated the theme (which will overwrite your changes, hence child-themes are a better idea for exactly that reason)

it doesnt matter though. from what i can see your theme provides a place somewhere to add custom css anyway, so i would suggest you just add it there

i.e add

@media screen and (max-width: 320px)
.wppizza-ingredients ul>li {
width: 99%!important;
}

(you might have to play with the max-width: 320px – perhaps make it ‘max-width: 350px’ or indeed ‘max-width: 400px’)

max-width: 320px is just educated guess here….