There are several threads on this problem on the site. As there are different reasons for it, a quick read through will probably find your problem.
Once again I find myself resorting to the 'try searching before starting a new thread' position. I do have a couple of reaaons for this, not just the 'don't be so lazy and and self-entitled', but the one most people miss is this; owners of websites pay for server space. Starting new threads ,expecting people to write the same suggestions all over again, rather than taking 30 seconds to do a search, eats up that space. Which for me ( as a website owner) is a behaviour that twists my melon.