I imported a Collada file created on Photoshop (turning a png into 3d plane), then extruded it in Blender. The reason for that is that this is a complex object to create with curves myself so I figured it's a faster approach.
Then I try to cut through some objects with this extrusion using the boolean modifier - difference, but I never seem to get this to work properly. Either getting "Cannot execute boolean operation" or it just won't cut the objects at all.
Tried modifying the boxes with the imported object as target, and the other way around too... I tried to use the knife project by selecting a box and the imported project but I get an error on "no other selected objects for projection" error. I tried removing doubles and fixing the normals. Nothing helped so far...
What can I fix for that to work? This is my first Blender project btw... Please don't mark as duplicate because I already mentioned that I perofrmed the actions described in other posts and it didn't help.

