Error when validating a constraint rule in product config

Hi this is the error encountered

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Siebel
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[1] Error invoking service 'Cfg Web UI Service Loader', method 'LoadCfgUIService' at step 'Go to UI'.(SBL-BPR-00162)
[2] Unable to load message 0x1()
[3] Error getting new worker.
Fatal error completing model.
An internal error was encountered:
  [EvalCSSDatum ]: Apply attempted to call a non-functional object.
while processing this rule:
  Residential Voice Service RVS Product's Rule Testing 1 ASIA:
Rule String is...When((the attribute Universal Service Order Code (USOC)CAD OR the attribute Universal Service Order Code (USOC) =ABA) and (selection of Ground Value PG13R from Service)) requires selection of Lifeline Discount RXXXX from Billing...