Unable to open App Store on iMac

Wondering which MacOS version you are using on your iMac.

Eg: You may want to check if there are "improved security" / updates waiting to be installed.

For recent MacOS versions:

choose Apple menu  > System Settings, click General in the sidebar (you may need to scroll down),

then click Software Update on the right.

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• Else: If you don’t have System Settings in the Apple menu ,

choose System Preferences instead. Then click Software Update in the window that opens.

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You may want to check that you are signed in (to your iMac) with your correct Apple ID:

See how to: Sign in with your Apple ID - Apple Support

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If you still need help: Apple support has an article online (link below) that may be helpful:

If you see "Cannot connect" - Apple Support

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More trouble-shooting:

If you can't download or update apps on your Mac - Apple Support

All the best :-)