Emails you if an account stops recording conversions, or a key ("primary") conversion action goes inactive or is removed. Conversion tracking is how Google knows which clicks turned into leads or sales - if it slips, automated bidding loses the signal it relies on and performance decays quietly. Catching it fast is what keeps Smart Bidding on track.
Account tracking switches off - the account-wide conversion tracking status flipping to off. On by default.
A primary action goes inactive / removed - any conversion action marked as primary for its goal that is no longer active. On by default.
Checks hourly; 24-hour cooldown.