I am unable to connect to App Store on old MacBook Air Running Mountain Lion

Apple-Expert wrote:

On old versions of macOS, the keychains for accessing the web are outdated. You can try use Firefox or a browser that does not use WebKit to access the web. You can see this website for more information:

https://apple.stackexchange.com/questions/405578/how-can-i-browse-the-web-on-very-old-versions-of-mac-os

You can either go back to a newer version of macOS (I believe minimum is High Sierra), try update the keychain (I failed doing that before even though I followed the steps required). If you are struggling to update your macOS version, you can get free help at an Apple Store.

Good try but it will not solve the Non Access to Apple Apps Store to upGrade back to macOS 11 Big Sur

https://support.mozilla.org/en-US/kb/firefox-mac-osx-users-esr#:~:text=If%20you%20want%20to%20keep,maintain%20Firefox%20on%20those%20versions.

Part 1 of 2

To perform this action will require booting from a Bootable Installer. 

The Bootable Installer can Only be performed on an Apple Computer 

This will have to be performed from a Qualifying Computer to run the version of macOS to be made on the Bootable Installer.

Example : Bootable Installer of Big Sur would have to be done on a computer that Qualifies to run Big Sur.

Notation: If the computer being used to perform this action is Too New or Too Old to qualify to run the version of macOS - this computer can’t be used.

Alternative is, to gain access to a Qualifying Apple Computer from a family member, friend or associate.

Part 2 of 2

Shutdown computer and disconnect all external drive Except the newly created Bootable Installer.

Restart and immediately hold the OPTION key until the Startup Manager appears and choose the USB Drive. 

It will present options >> Disk Utilities >> View >> View ALL attached Drives. 

Choose the Upper Most Drive ( not the volumes indented and list below ).

The drive normally is called Apple Media or Apple SSD - that is the drive to Erase and format as APFS with the GUID Partition Map. This applies to macOS 10.14 Mojave and above. 

Once that is done >> backup out of Disk Utilities and choose install macOS. 

Follow the prompts and it may automatically reboot several time. 

Upon a final reboot - Setup Assist will present with the newer version of macOS.

You can use Setup Asset and point it to the Time Machine Backup Drive. This is a One Time offer. Thereafter you will need to use Migration Assist 

On old versions of macOS, the keychains for accessing the web are outdated. You can try use Firefox or a browser that does not use WebKit to access the web. You can see this website for more information:

https://apple.stackexchange.com/questions/405578/how-can-i-browse-the-web-on-very-old-versions-of-mac-os

You can either go back to a newer version of macOS (I believe minimum is High Sierra), try update the keychain (I failed doing that before even though I followed the steps required). If you are struggling to update your macOS version, you can get free help at an Apple Store.