Forma Co2 Incubator set issues

Dear All, We have a Forma Co2 incubator Model 3111 that indicates "replace Hepa",which we have done.The problem is when we want to enter the settings to change the new value nothing happens.In addition to that the incubator's co2 runs for approximately 5 minutes at 5% then goes into configure mode.When it enters this mode,there is no co2 pumping but the temperature works fine. Can someone kindly please advise?. Thanks, Charles.