Vous n’avez pas les droits suffisants pour accéder à cette page

This can happen after changing the wp_ prefix in the wp-config.php and in the database table names. This can be useful when you want mulitple WordPress instance in a single database.

However some options need to be adjusted in some of the database entries:

• <prefix>usermeta :
  • wp_capabilites => <prefix>capabilities
  • wp_user_level => <prefix>user_level
• <prefix>_option :
  • wp_user_roles => <prefix>user_roles\

Reference

https://blog.juansorroche.com/wordpress-vous-n-avez-pas-les-droits-suffisants-pour-acceder-a-cette-page