...

For the other users, the “update user profile” action can be used to refresh their profile & timezone information.

Error: “Message not sent because outside 24 hours”

This limit applies to meta channels(Messenger, Instagram, WhatsApp). If the user hasn't engaged with your bot for the past 24 hours.

You can’t reach them directly. For WhatsApp, you will need to send a template message, for Messenger, you will need to send recurring notifications or one-time notification.

There aren't any good options to reach the Instagram user if they are outside of a 24-hour window. A work around is to gather the email of the user and reach them out via email.

More information here:
https://developers.facebook.com/docs/messenger-platform/policy/policy-overview/