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Most likely it is a Time and Materials Blanket. For time and materials blankets it gets the fau from the job. So fau on the job needs to be fixed.
- Account - Fund combination is invalid and you feel it is valid - Check fmbilling expense_fau table. If invalid check ods datawarehouse. If still invalid then check GL System with Valerie's help. If still invalid advise the user to check with accounting.