How to update a status field on an entity that is below the Opportunity entity?

I have an Opportunity record.  When this record is closed as won, I need it to update that status field on a record from an entity that is below the Opportunity entity, called Sales Incentive.  I can grab the status from the Opportunity record and have it update the sales incentive record when the sales incentive record is first created, but after that I can't get it to update.  Any help is appreciated.

Thank you.