"Parent theme missing", but it's not

I created a child theme based on the yoko theme but I get this message:
“The parent theme is missing. Please install the “yoko\” parent theme.”

I made sure the parent reference is lowercase, I checked that the theme folder is in the right place, style.css is in there, @import reference is correct. I also checked the folder permissions on the server and set public to ‘read’ but still the admin page is telling me the theme is incomplete and to install the parent theme (which obviously is installed and even active).

Any other thoughts on how to solve this?