If you don't have your instruction booklet here is a download with a section on calibration ~ http://www.brinsea.co.uk/downloads34
If you have a known to be correct hygrometer I would pop that in too and see what it's reading.
Did you prime the pump tubing with water before wrapping it round and connecting to the rigid tube?
Thanks Yorkshire coop for you help. I didn't prime the tube but I know it is working because I watch the water go through the tube into the incy.
I will try recalibrating thanks for your help. Wish me luck I have another hatch on Friday. I use my brinseas as hatchers. Thanks again