Sometimes you can see the error next to the auto post-boosting rules:
This issue happens when Facebook revokes access to ad account due to security reasons and a user should renew an access token.
You can reconnect your FB profile and Insights using these links:
Note: post boosting rules run their checks every 15 minutes so wait for a bit to see if reconnection worked. Also if the rules have been turned off please reactivate them manually and make sure that every required setting is filled out.
Is the error still in place? Contact us in our in-app chat or at firstname.lastname@example.org