Contracts Expired Service

Hello,

Dolibarr is using version 17.0.2. Settings–emails I have set SMTP settings. I can receive emails about events. Settings-alerts-Expired service I set it to -15. My question is, I am creating a contract. It appears in the system when there are 15 days until the contract period. But I can’t get this information as automatic mail. How can I enable sending mail 15 days before the end of the contract period? I searched the forum but couldn’t find it. Please help me.