When the plant 'prays' at night, the leaves are not folding, they stay kind of upright. When leaves curl up that means the plant gets too much light and/or the air is very dry around it. Calatheas don't like much light, even a little of indirect is enough for them to be happy. They show it immediately so it is easy to move them to a different spot where leaves unfold again in an hour or so.
To raise humidity around your plant, you can use a humidifier or stand the pot on a tray filled with pebbles and water. Make sure the plant itself is not standing in water!

If you meant by folding the upright position of leaves don't mind my post. You have to know Calatheas mostly do what they want, not praying every night haha!

Yes.. I meant the upright prayer position. They are having a prayer marathon!

Mine do that at night, but also when they're too dry, or the air is hot and dry, or else when the sun hits them. They do like their moisture, but not soggyness.