Couple of questions here. First as in the title, I have placed some invisible chair markers (furniture) but player can't sit on them, even the ones named .....player. Why is this and can it be changed?

Secondly I have made some new chairs, statics, and would like to know how to change them so they are furniture and can be used by player and NPCs. I tried duplicating an existing chair that is furniture and changed the model to my own but the markers disappear. Anybody help me with this please?

Thanks.

The vanilla invisible chair has no collision, so the activate prompt does not appear.

I made an invisible chair from it for my own use some time ago. It has a simple cube collision. You may use it if you want.

https://www.dropbox.com/s/dslsw8skgvvhei5/TamInvisibleChair.nif?dl=0

How did you change the model of the chair? It needs to keep the BSFurnitureMarkerNode. I simply use existing furniture and copy my NiTriShapes there.