General Styling not aplied

Hi, I just tried making changes to the styling of H1 to h6 under the Advanced Styling, they are not getting applied whatsoever though the back office tells me “Alright sparky! ”
… and then I tried to change the main font under General Styling.. same issue: No change whatsoever.. Though the back office tells me Sparky bla bla bla..again !

I never had issue until now.. but I have not tried changing anything in there for a long time as this site has been online for a couple of years and never really needed to make styling changes. So I have no idea since when this functionality broke in my site.

So what do I do now ?!?