Hi !!
I thought that sending you the stagging site would help you find the problem, but the error is not coming from the autooptimize plugin. That plugin is not on the live site. The live site is rioandlearn.com.
As soon as the page opens, you can see the main slider that has the ok symbol. If you want, I'll pass you a password so you can find the error.
I can see the same CSS but its not coming from the autoptimize plugin on your live site.
That CSS must be added as custom CSS.
Can you please share admin access details for the production site and let me see and try to find where that custom CSS is coming from.
*** Please make a FULL BACKUP of your database and website.***
I would also eventually need to request temporary access (WP-Admin) to your site. Preferably to a test site where the problem has been replicated if possible in order to be of better help and check if some configurations might need to be changed.
I have set the next reply to private which means only you and I have access to it.