the wheels are not hard to turn, you probably have the top and bottom pressed together too closely and its restricting the wheels. Also it is designed to be a tight fit so no glue is used, you may need to get a mallet or something to knock the pieces in place
Other Issues:I really like this counter but there were a couple issues.
The connectors were too big and I could not get them to go into both plates. I just shaved the edges a bit to jam in.
The wheel does not have enough space for your fingers to turn the numbers. If the back plate was narrower I think it would solve this.
I hope the design changes a bit because I would use this as my primary counter.