|Are you saying that your laptop has no button centre top on the touchpad?|
There will (or ought to) be an indicator light (like a small led top centre of the touchpad; and immediately below is the on/off (enable/disable) switch for the touchpad.
Refer to page 2-5 in the manual to which I linked you in my earlier post. It shows the exact location of the indicator and the touchpad on/off switch/button.
Also check the touchpad settings/preferences as outlined in the text area below the image of the touchpad area - as shown on page 2-5