Can't assign blender .fbx file to static mesh component


i have a little trouble. I made a BP with static mesh component to individually assign static meshes for child actors. Also I made some .fbx files in blender.
Now my problem is, that only some of the fbx.files I can assign to the static mesh component in the details panel. Others won’t appear. The panel shows me all of the files as static meshes, and also when I try to drag and drop the files from the content browser in the static mesh dropbox, the box appears with a green bar, but that was it. I can’t assign them. Now I am a little bit confused, what I have done wrong. Also I was going through the same export/import proceed.
Hopefully I described my problem the right way.

I wish you best luck and have a nice day,
yours Marc

I have found the issue. I had used the 4.25 version, with the 4.26, which I have installed afterwards, the problem was fixed. I guess there were some incompatibilities with blender .fbx files and the 4.25 version of unreal.
Have a nice day and good luck,

yours Marc