Hello, thank you for posting in the Microsoft Q&A community.
The main reason activation or key entry fails on Evaluation media is that evaluation builds (SKU: IoTEnterpriseSEval) are designed strictly for temporary 90-day testing purposes. Evaluation media contains hardcoded licensing restrictions that prevent direct conversion to full production licenses simply by entering a Multiple Activation Key (MAK), KMS key, or OEM product key via Settings > System > Activation or slmgr.vbs.
Depending on your goal, please follow the resolutions below:
Solution: To permanently activate the operating system with a production key, you must transition from the Evaluation SKU to the standard production SKU (Windows 11 IoT Enterprise LTSC 2024):
- Obtain the full production ISO for Windows 11 IoT Enterprise LTSC 2024 from your Volume Licensing Service Center (VLSC), Microsoft Admin Center, or authorized OEM distributor.
- Mount the ISO file directly within your current Evaluation installation.
- Launch
setup.exeto perform an In-Place Upgrade / Repair Install, ensuring you select Keep personal files and apps. - After the installation completes, open Command Prompt as Administrator and execute the following to apply and activate your license:
slmgr.vbs /ipk <YOUR_PRODUCT_KEY>
slmgr.vbs /ato
If you are currently evaluating the platform and require additional testing time before deploying production media, you can reset the 90-day evaluation period up to 3 times (providing up to 270 days of total evaluation time):
- Open Command Prompt as Administrator.
- Run the rearm command:
slmgr.vbs /rearm
- Restart the computer for the extended evaluation counter to take effect.
I will follow up on this thread to ensure your issue is resolved. If this helps, please consider hitting "Accept answer".
For official details regarding licensing and deployment, please consult: