This occurs if the the api key, sharing link or password has changed on your base.
To fix this you need to update your api key or sharing link.
Navigate to: [your portal URL]/admin/onboarding/connection and you'll be able to re-enter your API key.
This also applies if you are unable to see any records showing on your portal, even though an update has been run successfully, please check that you have not changed your api key.
Please do not update the api key and sharing link if you have made major changes to your base (add/remove tables and fields) this will result in the loss of layout in your app.