Our mac book air turned suddenly off and now won't turn on black screen

Depending on the total issue, you may have to try a power reset, in partial attempt to

troubleshoot the symptom you vaguely describe. ~ Sometimes a power management

re-set may help. In this Support article and there is a long list of things to try ahead of

the actual reset. I suggest you try each of them, logically, before the actual re-set itself.

..Note the last line in the above (copied from main link below) is the last item to try here:

• How to reset the System Management Controller (SMC) on your Mac - Apple Support

Also, if there is a chance the unit may be able to start, the system may have issues;

you could try Safe mode startup. It may not work if there is hardware failure issue:

• Use safe mode to isolate issues with your Mac - Apple Support

Another different item to try may not help in this situation: IF the battery or hard drive

has failed, nothing may happen at all. ~ See an Apple Authorized Service Provider.

Under certain conditions, other re-set instructions here may help: [ NVRAM or PRAM ]

You may need to see about setting an appointment for inspection &/or diagnostic

so the expert Apple authorized service can see what can be done to fix the unit.

There may be something a genius or technical person may try in retail Apple Store.

• Make a reservation at an Apple Retail Store Genius Bar

Usually by appointment the 'genius bar' may schedule you in + that could be weeks.

For your options contact an Apple Authorized Service Provider or Apple Retail Store.

Depending on your location or region, other options may exist to contact Support.

• Contact Apple for support and service - Apple Support

or Repair and Service (log-in to see Apple products list, etc)

Because there may be hardware failures &/or software problems, there isn't

much else to suggest from here. Sorry to not be more helpful in this matter.

There supposed to be a support App for iOS devices that may be helpful

if you had an iPhone or iPad with iOS11. I've not found link to check it.

PS:

iDid find the link to get 'Apple - Support App' for iOS devices from

the iOS App Store that may be helpful ~ to check schedule options.

Apple Support on the App Store - iTunes - Apple

Download Apple Support and enjoy it on your iPhone... to my account in the Apple

Support App. It's not attached to 'my Apple ID' or personal... United States.

https://itunes.apple.com/us/app/apple-support/id1130498044?mt=8

..if you had an iPhone or iPad with iOS11. I've not gotten it yet

and only my recent SE iPhone meets the iOS level requirement.

Good luck & happy computing! 🙂

{..edited to correct app site region URL..}

Check your Wifi connections.