If the anime is in your “Watching” or “Planned” list, you will receive notifications on new releases (currently twist.moe based).

Sequels of your completed anime will not cause a notification on episode release if they are not in your Planned/Watching list. You can either add the sequel to your Planned list or simply click the three dots “…” on your profile page and access the sequels of my completed anime page to get an overview of what you might have missed.