Vor/Loc establishing problem

Hi all,

I'm being driven mad by trying to establish on a localiser using vor/loc button. the airport in question is LIEA in Sardinia-Italy, using ILS runway 20. I have set 204 for course, 110.15 Loc freq I am at the correct intercept altitude of 3000' (I'm sure that's what the chart is telling me), but the button won't light up. I can get the Glide path, {specifically) not glide slope (G/P is displayed not G/S) and I am unable to autoland. I tried flying the approach with and without VoxATC  (and with vox vectoring me and full ils approach) to no avail.

I'm using the PMDG 737 800 and have had a similar problem at Aberdeen (if I remember) but everywhere else is fine.

If anyone can throw any light on this, I'd be grateful, or if anyone is looking for a destination and fancies trying it, I'd be interested if it's the same for you!

Thanks.

Rob Padgham