phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '21e8df9ed3d432bbfd78dd5059c99959' for key 'phpbb_sessions.PRIMARY'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('21e8df9ed3d432bbfd78dd5059c99959', -1, 1770659063, 1770659063, 'd849d88f', -4, 0, 0)

Line : 187
File : sessions.php