MacBook Air not turning on

i have a 2011 MBA, the battery is a little shot and the trackpad doesn't always do it's thing, but generally it works fine if a little slow.

so now it won't turn on. nothing. green light on the charger - but pressing the power key does nothing. all the combinations of shift/cmd/crtl/etc have zero effect.

apple genius weren't available today (will try tmrw), however a member of staff told me it could be the power charger. i have a 85w. this should be a 45w charger apparently, however, i've used this 85w without any problems thus far. i also read this: You can use a compatible higher wattage adapter without issue, but it won't make your computer charge faster or operate differently. Lower wattage adapters will not provide enough power. - Find the right power adapter and cord for your Mac notebook - Apple Support -

i tried a colleague's 60w charger, but still no joy.

can anyone suggest anything else? please?

thanks,

J 😕