hello ive been trying to do star trails from stacked images but when I press lighten nothing happens

Make a new layer under any one of the star trail layers, and fill it with black.  That will prove whether the star trail layer are working. 

Select a scatter brush and paint with white on the top most layer.  That will also prove things out for you.

Create a new document and do some test with it to rule out an issue with the original.

Open Panel Options in the Layers panel and set thumb nail size to large, and take a new screen shot.  Paste it here at full res so we can actually see how things are set.

Please don't use your phone to take the screen shot as we don't have enough detail to assess anything.  If using Windows, use the Snipping tool (hit the Windows key and start typing snipping

Or install Green Shot (which is what most of us use if we are using Windows systems)

https://greenshot.en.softonic.com/

You sure the stars are on the top layer?

Are all the layers in Lighten blend mode? This is a per layer setting, not a global setting.