What do you do if the Convertible top of a 1998 Porsche Boxter will not go up?

If the top won't close with the key turned to "on" or with car running and the parking brake engaged make sure the parking brake light is on. If it isn't your parking brake sensor is bad and you need to go to a shop to have it replaced. In the mean time try releasing and reengaging the parking brake a couple of times to see if you can get the sensor to trigger and the brake light to come on. If that works don't put the top down again until you get the sensor replaced. Or it might just need a new fuse.