Credit memo type not found

To implement the solution, please execute the following steps:

In Projects, navigate to Setup > Implementation Options > Billing tab

Make a note of the value of the "Invoice Batch Source"
Sign in to the application with an Accounts Receivable responsibility.
Navigate to Setup > Transaction > Sources.

Query the Invoice Batch Source found above.
Ensure that the batch source is active.
Ensure automatic invoice and batch number are off.
Ensure that there is a value for Standard Transaction Type. Make a note of this value.
Navigate to Setup > Transaction > Transaction Types.

Query the Standard Transaction Type found above.
Ensure the following settings or options have been selected:

Class = Invoice.
Open Receivable box is checked.
Post to GL box is checked.
Creation Sign = Any Sign.
Start and End Date: The invoice date of the problem invoice must fall within the effective date range of the Transaction Type.
Credit Memo Type: This must have a value assigned. If it does not assign Projects Credit Memo
Repeat the above checks for the Credit Memo Type.
For the Credit Memo Type, the class should be Credit Memo rather than Invoice. All other checks are the same.