A student on Udemy had the same question as you. I’m copying and pasting @Marc_Carlyon’s answer in case you are not enrolled in our course on Udemy:
Another solution we had with bridges and things is to add an object to the stairs and make it not bakeable by the navmesh and turn off its mesh render so its invisible to the scene but also creates a ramp for the player to go up.
The reason the enemy makes it up stairs is as i am sure you have seen in your tests is that it follows the navmesh which is not on every step.
This thread might also help with the stairs problem. However, I didn’t download and check the student’s project.