Hi, using on-screen keyboard at the moment and its really slow

So my keyboard was almost out of batteries, so I changed them and now my keyboard won't reconnect

My wireless mouse is working fine

I know I have to press the connect buttons on both my keyboard and receiver, but I can't find the button on the keyboard!

I am using standard 101/102 key on Microsoft natural ps/2 keyboard, and I can't find a manual

Any help wold be appreciated