help with coil modeling - results are not reasonable

Hi
I am trying to simulate a coil.
ID- 12mm
turns -15
wire dia - 0.5mm
space between wires - 0.2mm

according to wheeler aproximation (and calculators online) - the inductance need to be ~5.5uH.
the problem is that when using hfss I get 0.02uh
I tried to solve it by changing ports shape, mesh solver.

Why is it?
What can go wrong in that simulation?
any help will be welcomed,

I also added the hfss file...
flat_coil2.rar

The estimate 5.5 uH seems correct to me. I don't know HFSS, but it seems you have a short circuit close to the ports. Is the squared external box non-conductive ? Can't you eliminate it and see what happens ?

Hi
thanks but this is not it. the squared external is conductive but it just there to set the ports for the coil. this is how you set a port in hfss.
I think the reason is the distance from wire to wire - the gap of the spirals.
but thanks anyhow,