No style imported on Formats sub-menu with gutenberg block

WordPress 5.6
PHP 7.4
Theme : child of “WP Bootstrap Starter” https://fr.ww.wp.xz.cn/themes/wp-bootstrap-starter/

Hi,
I have a problem with importing styles into the editor with Gutemberg blocks. The submenu is empty: screen shot => https://i.imgur.com/K2DXsj0.png

Strangely, the plugin is fully functional with the classic editor in my customs post types (ACF). Screen shot => https://i.imgur.com/G3LKvkF.png

Someone can help me ?
Merci.
Ludw_