Seems like some others developed the site. If you are coder/programmer try the below
- Login to hosting
- Open PHP My Admin or any mysql UI tool
- Open Prefix_users, usually this will be wp_users
- see list of users and check if you have admin permissions. Sample below
user_id – specific user id
meta_key – wp_capabilities
meta_value – a:1:{s:13:”administrator”;s:1:”1″;}
then save the DB record. Else get programmer support