Revenue Cloud Advanced: Import Lines fails with MissingRequiredFieldValueException in RevenueTransactionErrorLog

Follow the causes in order. The same CSV importing on one quote but failing on another almost always indicates a per-quote required-field difference or a trigger error path.

Cause 1: A required field on the target Quote is null
1. Open the failing quote and the working quote side by side.
2. Navigate to Setup > Object Manager > Quote [Quote] > Fields & Relationships and identify every field where Required is selected, including any layout-level required fields and any validation rules that enforce non-null values.
3. On the failing quote, populate every required Quote field (commonly Account [AccountId], Pricebook [Pricebook2Id], Expiration Date [ExpirationDate], Status [Status]) with the same values as the working quote.
4. Re-run Import Lines on the failing quote.

Cause 2: A required field on Quote Line Item is missing from the CSV or default
1. Navigate to Setup > Object Manager > Quote Line Item [QuoteLineItem] > Fields & Relationships.
2. List every field marked Required and every Validation Rule on QuoteLineItem.
3. Confirm the CSV column headers exactly match the API names of all required QuoteLineItem fields (header row is case-sensitive against the Field Name on the Import Column).
4. Add any missing required column to the CSV and the matching Import Column on the Import Format record. Set Active [Active] to true on the Import Format.
5. Re-run Import Lines.

Cause 3: An active Apex trigger on Quote, QuoteLineItem, or Product2 throws an exception during the PST insert
1. Navigate to Setup > Apex Triggers and list all active triggers on Quote [Quote], QuoteLineItem [QuoteLineItem], and Product2 [Product2].
2. Open the RevenueTransactionErrorLog [RevenueTransactionErrorLog] record and check whether the error class is TriggerExecutionException (Cause 3) or MissingRequiredFieldValueException (Causes 1 and 2).
3. If TriggerExecutionException, in a sandbox deactivate each custom trigger one at a time and retry Import Lines after each deactivation to isolate the offending trigger.
4. Fix the trigger to handle null inputs and bulk inserts coming from the Place Sales Transaction API, then re-activate it.

Cause 4: The Data Processing Engine definition required by Import Lines was cloned but not activated correctly
1. Navigate to Setup > Data Processing Engine.
2. Open the Import Lines Data Processing Engine definition you cloned.
3. Verify the API name and Process Type are unchanged from the out-of-the-box template.
4. Click Activate. The definition must be in Active status before Import Lines can succeed.

Cause 5: The Product referenced in the CSV is not on the quote's pricebook
1. On the failing quote, note the Pricebook [Pricebook2Id] value.
2. Navigate to Setup > Object Manager > Price Book Entry and confirm an active PricebookEntry [PricebookEntry] exists for every Product Code in the CSV against that pricebook.
3. Add missing PricebookEntry records or correct the Product Code in the CSV.

Confirm the issue is resolved by re-running Import Lines on the previously failing quote with the original CSV and verifying the quote line items are created and no new RevenueTransactionErrorLog record is written for the transaction.