Losing a product key for a legacy product is stressful, but you have options.
Open the Deployment Manager MMC snap-in on the CRM server to view license details and current keys. dynamics crm 2016 product key
Sarah's expression turned thoughtful. "I think I might have a lead," she said. "I remember working on a project with a similar product key a few years ago. Let me check my old notes." Losing a product key for a legacy product