ERR_VALIDATION_RULE on Salesforce: Validation rule error. Root cause: A Salesforce Validation Rule is blocking the record save. Validation rules enforce business logic constraints on field values — such as requiring a field to be populated when another field has a specific value — and the data submitted via API violated one of these rules. The error message from Salesforce typically identifies which validation rule fired. Step 1: Review validation rule. Check rule formula Step 2: Understand error. Read error message Step 3: Fix data. Correct violating data Step 4: Retry save. Attempt save again