Reasons: Your accounting platform details, like product names, classes, or categories selected as conditions in the rule have been deleted/made inactive/changed or some payment platform details are not applied correctly which does not allow the rule to execute.
Solution: Check the smart rule execution and find what prevented the smart rule execution.
Go to your Synder company → go to Categorization rules on the left-side menu → select Executions → click on Show execution to check what rule failed and what exactly failed in it.
As you see from the 3rd screenshot, the rule failed because Synder was not able to apply an action, i.e. find the category.
2. Modify the smart rule, transaction, or other necessary details to make it work.
E.g., as for this case, check whether the category the fee [Expense] should be applied to is active in your accounting company. And if it is not, make it active.
Then go back to the smart rule that failed → find the transaction(s) that was (were) synced incorrectly → roll them back and once they have deleted statuses, sync them again to apply to the needed category and check the result.
Check the smart rule execution and the synchronization results in your books by clicking Show in QB.
Congrats! Now the rule will work smoothly.