Question about Rapoo 9500M

Hi everyone, I connect the mouse and the keyboard via USB dongle to my notebook. The mouse works perfectly, but the keyboard does not react at all. I have already replaced the battery and it looks like the keyboard is locked. I know that there is a "key combination" to reactivate the keyboard, but I can't find it anymore:( Can anyone help me? It was a simple "key combination" to unlock...