We won’t be able to tell what might be the issue since you didn’t provide your current setup. But here are the steps you need to follow in order to achieve your goal:
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Create a new AI controller blueprint
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Create a new character blueprint
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Inside our character blueprint, navigate to the Details window on the top right while Self is selected on the Components window
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Assign our AI controller from the dropdown menu next to the AI controller class text, and make sure that the auto possess AI setting is set to placed in the world
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Head to the Event Graph and place the AI Move To node after Begin Play
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Insert your desired destination into the Destination pin of the node and make sure to keep the acceptance radius low
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Head back to your level and add a Nav Mesh Bounds volume into the scene
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Adjust the Nav Mesh accordingly, by making sure that it covers all of the areas you want the AI character to be able to navigate to. You can press P on your keyboard to see if you got those areas covered.
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Finally, place the AI character into the scene by dragging the blueprint class from the content browser
Now your AI character will be able to move with no problems 
If you struggle with any of the steps or you can’t produce the expected result, you can share you setup while making sure to provide all of the necessary details for us to take a look at.
Hope this helps! 