How do I change my Apple iPhone 12s folder name.

How do I change my Apple iPhone 12s folder name. When I first got my iPhone it let me title my own file on my home screen I mean my folders. Now I went to add a new one and it said productivity so I went to change it because it has the option to rename it so when I ask out the old name productivity a line blinks in the middle and no keyboard comes up. So when I log back out or back back out it puts the name productivity back again because it Hass to have something so it reverts back to the original name.

[Edited by Moderator]