Collision for a house - actor merging

I own the medieval village asset, so I went to their demo map, copy and pasted a house from there (it’s made up of multiple components, like a floor, stairs, roofs… etc)
then copied it into my game, and did an Actor merging on them, to have the entire house as one static mesh.
Everything seems to be working rather good, except for collision.
Any collision that I try to apply doesn’t work, because it’s not precise enough, so it blocks the doorway, or even prevents getting anywhere near the object.
So, I tried the Auto convex collision with max hull verts and accuracy at maximum, and it still blocks the doorway.

I tried using the use complex collision as simple, and it just doesn’t seem to work. Simply no collision at all. I set my mash to static, and no lack still.

What am I doing wrong?