Yes, the key should be in the switch housing somewhere.............I had the same once on my Twinny, played about with it, gave up and then it shut all by itself. I oiled all the hinges, runners etc and its been fine for years since :d
This guy's breaking three 155's, one of which appears to be a running Silverstone, in Black - if you follow the link to eBay, then view sellers other items, and the o/s rear light cluster, you see the Silverstone sticker and spoiler. I wonder if he know's what he's breaking??
I had this problem. I used to run with the panel hatch removed as the only way to close it was to 'fiddle' with the wiring, connections and the relay.
After a while it worked.
Fitting a new relay sorted it properly, that might be your answer. When you are sourcing one, note the make of the sunroof motor as there are 2 different types in use.