There may be something mechanically wrong with the hybrid bike, but you comment that your knees hurt when riding at moderate speeds is a major red flag! This often indicates your saddle is too low, and having to low of a saddle makes riding much more difficult.
You need to go to a bike shop with staff experienced with fit issues. Get them to check out the bike for damage at the same time. Also make sure your tires are pumped up to their maximum pressure before you go for a ride on the road. I ride a hybrid with CX tires and, while it is not as fast as my road bike, it is not a struggle to keep moving at 10 mph nor does it make my knees hurt.