Hi @Nikolaus Pusterhofer
Thank you for posting your question in the Q&A Forum.
We understand that the product was not visible when you previously checked the Microsoft 365 Admin Center, and we know this can be frustrating when all you need is access to your product key.
To help you move forward smoothly, please note that all Volume Licensing features, including product key retrieval, are now handled exclusively through the Microsoft 365 Admin Center.
To retrieve your product key, please ensure your Volume Licensing Administrator follows these steps:
- Log in to the Microsoft 365 Admin Center with the account linked to your Open Value Subscription agreement.
- Go to Billing > Your products.
- Select the Volume licensing tab.
- In the Products and services section, click View downloads and keys.
- Locate Exchange Server 2019 and select the product name.
- In the side panel, select the Keys tab to view and retrieve your product key.
If the key still doesn’t appear after following these steps, it is most often related to permissions or an account linking issue:
- Check Permissions: To view Volume Licensing product keys, the user must have either the Volume Licensing Administrator role or the Product Keys Reader role. Please ensure the correct role has been assigned.
- Contact Microsoft Volume Licensing Support: If permissions are verified and the product still does not appear, the next step is to contact Microsoft Volume Licensing Support directly. They are the only team who can confirm the status of your agreement, ensure it is linked to the right account, and provide the product key directly if needed.
You can find the official guidance page for your reference here: Find and use product keys for volume licensing | Microsoft Learn
We hope this information helps you resolve the issue promptly. Please feel free to update the thread if you need any further assistance.
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