Fails With Error UTIL0020 Invalid Concatenated Segment

1. Navigate to Setup -> Financials -> Flexfields -> Key -> Segments

2. Query for the structure (Chart of Accounts), by entering:
      Application = General Ledger
      Flexfield Title = Accounting Flexfield

3. Unfreeze the Flexfield Definition.

4. Confirm that all Segments in the structure are Displayed and Enabled.
     All segments must have the checkbox ticked.

5. Recompile the Structure.

6. Run the posting program again.