If a record couldn't be updated when a Customizable Rollup ran, what should the consultant check first?

When a Customizable Rollup fails to update a record, the first thing a consultant should check is whether the Target Field has a validation rule. Validation rules are designed to enforce specific constraints or conditions on the data within a field. If the data being rolled up does not meet the criteria specified in a validation rule, the update will be prevented, causing the rollup to fail. Therefore, ensuring that there are no validation rule conflicts is crucial in troubleshooting issues with Customizable Rollups.

Other factors, such as whether the Target Field exists, whether it is an NPSP field, or if the Target Object is a custom object, may also be relevant, but they do not directly address the critical reason for the failure to update as validation rules do. If a validation rule is in place, it will take precedence and block any unsuccessful attempts to modify the record, making it the most direct and effective check to perform initially.