1st: what exactly doesn't work?
In other words are you getting an error? (If so what's is exactly?)
Or you can't access the page? (do you get any error?)
2nd: what version of SMF are you using?
3rd: are you using the default theme?
If no try with the default first and see if it works.
4th: are you using English or another language?
If another language, please try with English and see if it works.
5th: do you have mods installed?
If so can you list them all?