Where is the air blend door actuator located?

All of the blend door actuators are vacuum controlled so if all of them are not working I would look for broken vacuum lines (small) under the hood that go from the engine to the fire wall.

Here is a guide that will help:

https://www.2carpros.com/articles/air-vents-stay-in-the-defrost-position

Check out the images (below). Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.