If your Instagram Direct Messages aren’t appearing in Blabla, you may see this error:
This usually happens because the required permissions haven’t been enabled in your Facebook Page settings.
How to Fix This
Log in to your Facebook account that manages the Page linked to your Instagram.
From the top-right menu, click Settings & privacy → Settings.
Scroll down to the Permissions section in the left-hand menu and select Linked accounts.
Choose Instagram.
Make sure Allow access to Instagram messages in Inbox is enabled (see screenshot below).
Once this setting is enabled, Blabla will be able to sync and manage your Instagram DMs.