There are steps that you need to check:
Your Facebook Page is not connected with an Instagram Business/Creator. Please connect to your Facebook Page, you can follow this guide Connect Facebook Page with Instagram Business/Creator.
Your Facebook Page access still reviewing or not confirmed. Please review/confirm via Facebook Page Settings or Instagram Apps - Edit Profile.
- You are not an admin role on your Facebook Page. Please make sure you are admin on your Facebook Page by following this doc.
- Try to reconnect between your Facebook Page and IG account, and also reconnect between your Qiscus Multichannel and your Facebook Page.
- Ensure to enable allow access to messages in your IG Business Account