If my zapper did not work,I would see about returning the zapper. It could also be that the particular zapper you received might have been defective. It happens. If a zapper is working right, then you definitely should feel a difference within a few days, if you are using it correctly.
Did you use the 7-20-7-20-7 method? Did you use paper towels with salt water? Did you take probiotics afterward? Did you drink the right amount of fresh water when zapping? All of the above are important.
For additional information on zapping for best results, see: parasite Zapping and the Zapper.
Not all Psoriasis will be parasite related. Sometimes, if it is the only problem, it may be a nutritional problem.