Fuses are designed to stop the flow of power to a circuit whenever too much electricity is flowing through it. To do this, fuses utilize a special wire that will break under these circumstances.
Although many people believe that you can look through the top of a glass fuse to see if it is broken or not, this is not always the case.
If you believe a fuse is blown, the best thing to do is just replace it. If this restores your power, then you have solved the problem. If not, then you will need to call a experienced heating and air specialist to troubleshoot the problem.