centering menu items

Menu items in my theme were centered before I installed Mega Menu. On Mega Menu, I folloowed the first two steps here https://www.megamenu.com/documentation/centering-menu-items/ to keep them centered. But Menu items default to the left and I can’t get them back to center. Only thing I can do is individually move them to the right. What am I doing wrong?

(I turned Mega Menu off for now because I didn’t like the look of a leftside menu.)