No way to change Fontsizes in Enfold Child options / in Enfold it works

Hello support,
I urgently need help. I have a problem with enfold and enfold child which I can not solve alone. Unfortunately, I find no similar case here in the support forum. My problem is that I can not change the size of fonts used in the theme. I have disabled all plugins to see if a plugin is responsible. But without success. I then uninstalled enfold and enfold kind and reinstalled.

I activate the enfold theme I can easily change the size of the fonts. I activate the child theme I can not change the sizes. I’m going crazy and can not find an explanation how I can solve the problem.
The website should go online urgently, but I would like to make some visual adjustments.the functions.php and the individual CSS code are deleted.
Can someone please explain to me what causes the error, and how to solve this problem? I do not want to have to rebuild the website completely or install wordpress new.

I put the website in maintenance mode and created a userprofile in the private content for the moderators of this forum. If no access is possible please write me a short message.

Best Regards
Markus