How to add an additional domain on cPanel?

Question

WHM/cPanel

Your addon domain limit of 0 has been reached. The addon domain yunivir.ru was not added.

It was necessary to add an additional domain yunivir.fr, but it gave such an error. I, for the test, removed another add. domain yunivir.ru and tried to create a new domain, but still gave this error, and back to create a remote add. domain failed. How to solve this problem? Never worked with cPanel.