Hello Nelson Ortiz,
Thank you for your question.
To better understand the issue, could you please clarify:
- Where are you entering the product key (Microsoft Store, Microsoft account redemption page, or during Flight Simulator X installation)?
- What is the exact error message you receive?
- Was Flight Simulator X Gold Edition purchased as a DVD/disc version or a digital download?
The exact error and redemption method will help determine the appropriate troubleshooting steps. Additionally, older Flight Simulator X product keys do not always redeem through the current Microsoft Store system and may need to be used during product installation instead.
I look forward to your reply.