Hi Maru, it’s hard to tell from the image but there are two things I always try first when bevel’s don’t work.
1) Merge by distance. Go into edit mode and select all and hit F3 and type “merge” and select the merge option and then choose “merge by distance” as the method. Sometimes you have more than one edge, face or vertex in the same place and this can cause issues with bevels.
2) recalculate normals. Go into edit mode select all again and go to the menu at the top of your viewport. Select the mesh menu, go to “normals” and select “recalculate outside”.
Hopefully one of these two options will fix the issue!
