Why is my desk still tacky two weeks after finishing it with a polyurethane clear coat?
The poly simply needs to cure for a while. Even after it "dries" and is safe to work on, the solvents that keep the polymers in suspension aren't all gone; they'll continue to evaporate, and the clear coat will fully harden in time. Check the can for your particular product; it should have a full cure time. It could take up to a month if you laid on a really thick coat and it's humid in your area.

Contrary to intuition, you can wax furniture that has a poly coat, much like you can wax a car that has a clearcoat. Just pick up a can of Minwax, apply and buff, then let dry overnight. This additional protective coating will be temporary, but hard, water-repellent and slick.