Fuses are designed with a small wire that will fail of too much power flows through it. As a result, the electricity will no longer flow through this wire.
Although many people think that looking through a glass fuse will let you know if it is broken or not, this is not always the case.
If you suspect that a fuse is blown, the best thing to do is replace it. If this fixes the problem, wonderful! If this does not restore power, always call an electrician to come do some electrical troubleshooting.