Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello,
It might take up to 48 hours for the old subscription status to refresh in the backend. I would suggest that you wait another day to redeem.
If it still gives you the error, contact support. Only they can sort it out.
To get help, open the "Get Help" app on your computer (just search for it in the Start menu). or go to https://support.microsoft.com/contactus, Type "Billing" and press Enter. On the next screen, click "Contact support" at the bottom of the page, then choose "Microsoft 365" > "Manage my subscription". You’ll then see the option to chat with a Microsoft support agent who has access to your account to help review the issue.