[Ducati] Advice needed on spark plugs

[Ted]

Why can't I change the spark plugs on my 916?  

Seems a simple enough procedure that I have done 100s of times on my other bikes, but for some reason neither a standard spark plug wrench from my socket set nor the one that actually came with the Duc's tool kit seem work.  It feels as if there is something deep in the chamber that is blocking the wrench from seating down onto the plug.

Any hints or advice would be appreciated.

Thanks.