MacBook Air does not wake up when the lid is opened.

When we close the lid to put our MacBook Air to sleep, it does not wake up when the lid is opened. I can get the keyboard to light up, but that is all.

We have to hold down the power button to power off and then reboot to get it started.

I can choose to put it into sleep mode from the menu without closing the lid, and then I can wake it up by pressing the power button. But if I close the lid - same problem.

I have tried the procedures for resetting SMC and NVRAM and also reinstalled iOS - this has made no difference.

Is there anything else I can try before taking it to a service center?

Regards Stephan.