[help] My sitemap disappeared

Huuu what isi it ?

My sitemap disappered and google and others cant find it since today

While accessing directly by mydomain.com/sitemap here is the error I get :

Fatal error: Maximum execution time of 60 seconds exceeded in /home/decouve/public_html/wp-includes/post.php on line 3031

This occures only on one of my sites....

Seo plugin correctly installed (and reinstalled)

huh ?