Just installed the new 3.6 version of WordPress. I activated the WP Google Fonts plugin, and when I view my header fonts the settings seem to have been preserved, but when I try to access “settings” under the WP Google Fonts plugin itself (from my Admin screen in WordPress), I don’t see the font selections/choices. It’s blank below WP Google Fonts. Using a self-hosted version of WordPress.
flushing any caching plugins you might be running, as well as server and/or browser caches.
deactivating all plugins (yes, all) to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s). Sometimes, an apparently inactive plugin can still cause problems. Also remember to deactivate any plugins in the mu-plugins folder. The easiest way is to rename that folder to mu-plugins-old
switching to the Twenty Twelve theme to rule out any theme-specific problems.
manually upgrading. When all else fails, download a fresh copy of the latest.zip file of 3.6 (top right on this page) to your computer, and use that to copy up. You may need to delete the wp-admin and wp-includes folders on your server. Read the Manual Update directions first.