Double-clicking only happens when you press the mouse button twice quickly enough. If the second press is too long after the first, you’ll just get two separate clicks, not a double click. If you have difficulty pressing the mouse button quickly, you should increase the timeout.

If your mouse double-clicks when you want it to single-click even though you have increased the double-click timeout, your mouse may be faulty. Try plugging a different mouse into your computer and see if that works properly. Alternatively, plug your mouse into a different computer and see if it still has the same problem.