Make sure Z Reset position is 188. After build plate drops down, loosen all 4 screws under the platform and then tighten it back to touch the platform. Then tighten 1/2 turn more. (tightening is turning screwdriver clockwise)
for more information, follow leveling guide:
https://drive.google.com/open?id=1MeXCjGVIVvCN8XrciehLLfmdflCe3DazT6CqE1-7oew