When a Facebook scheduling shows the error message type: OAuthException, code: 200, message: (#200) Permissions error [HTTP 403], it means the social network identified a missing permission in the page management through the platform.
This happens because the user who performed the page integration process in mLabs did not enable the necessary platform access on Facebook.
To resolve this, it is necessary to enable our app's access within Facebook.
Below is how to perform the process and grant the necessary permission:
Access your Facebook account (it must be the account that performed the Facebook page integration in mLabs).
Click on your Profile.
Settings & privacy.
Choose SETTINGS.
Then click on Business Integrations (Link)
Locate the mLabs app and click REMOVE.
After removing it, return to the mLabs Dashboard and click 'Reconnect'
When returning to the connection, it will be necessary to update the account list again. Then, it is important to grant all permissions on the screen that will appear during the connection:
When finished, your permission will have been updated :)