restrict category to roles doesn’t work

I’ve installed your plugin because it’s what I’m looking for, simple and smart!

If I set [sp4ppcl_protect_page_with_login to the description of a category everything is ok, guests are redirected to login page and logged in users can see all posts in this category.

If I set [sp4ppcl_protect_page_with_login role=”author”] guests are redirected to login page and logged users (doesn’t matter if subscriber, author or even higer role) are always redirected to homepage.

I’m using this verson of WordPress: 4.9.6–it_IT.

Thanks in advance for your help,
Enrico