My kids got on my Mac and since the computer hasn’t booted up correctly. Has a white screen with a flashing question mark. Tried the command key and R. Nothing. Any ideas??

That question mark tells you the the computer is unable to find its operating system and cannot start up. Either they have done something to cause this or your hard drive is failing.I would next try the Internet Recovery Mode. Press the Command + Option R keys on restart. Tis is to enable you to download and install the original OS that the computer came with. If that works, you may then have to upgrade it to a newer operating system. If that fails, I would have the computer checked by a specialist.

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