Whenever I try to add manga to my complete, reading or wish list, from the Manga info page, it doesn't add to any list, or even show it adding it. (Usually it would do a Check mark if I added it to the complete page, or tell me it added the manga.)

Is this a bug or am I lacking something on my side?

Clear your cache and cookies then try again.

That was easy. Thank you! 🙂