Lets try to narrow down problem...
With the ignition on (no need to have the car running) pull up on the parking brake, does the "Park" indicator light on the dash come on when you pull up on the parking brake? If not, you have a problem with the Parking Brake Switch. There are a couple of threads about that here:
"Top wont go down" and here
"Hmmm.. Top Button dead"
I had a similar problem, my switch is fine, the connection was just loose. Sometimes a few quick pulls on the parking lever gets the switch working again.
If the Park light indicator does light up and you still cannot get the top to work there might be a problem with the relay. The Top relay (on my 99) is the big relay box, mostly covered by a white label with a black arrow, located up under the drivers side foot-well. Make sure it is not loose. Also check the fuse.
Beyond that other more experienced members will have to chime in with some other suggestions.
You could also do a search on this forum, in the
Rennlist Forum or in the
Renntech Forum.