Yes, it does, Have you entered the “rem” value after you entered the value in the customizer settings -> For example 1rem 0r 1.2rem. and there are two customize body font size which increases all the font size of the site and content font size which increases or decreases the font size of the content color. Can you state where do you put the font size?
When i see your site i found that you haven’t inserted you Main Content Area Text Size. Could you please sent us the log in details of the site to our email. so i could manually check what is wrong there as there is no problems in the font size selection.