Notify after 3,6,9 and then 12 months after plugin activation

You could try to set a Transient and set its expiration to 3 months. Once it expires, it can trigger a message or some other behavior that alerts the user about the timeframe.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)