While reading any series on mobile version, there should be three horizontal white lines on top right. If you tap that, there comes a menu bar, and the 5th option from that menu is □multi pages. Check if you have blue ticked it. If you tap on that box □ again, it will get unmarked and you'll be able to see the single panel like before.
But I've no idea if you are using web version/PC.

I don’t know what I did but now everything I read is like a full page and it is not split up anymore. (Like usually you click and boom next panel)