Hello Rodrigo R Moraes,
Thank you for posting in Q&A forum.
Based on your error message, your forest functional level must be 2008 or higher.
The domain functional level must be at or above the forest functional level.
In your screenshot, I can see the domain functional level is 2008 R2.
You can check the forest functional level by running commands below.
If forest functional level is lower than 2008.
You can upgrade your forest function level on the DC by right-clicking on the domain name in your AD management center and selecting the forest function level.
I hope the information above is helpful.
If you have any question or concern, please feel free to let us know.
Best Regards,
Daisy Zhou
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