Macos 10.8.5 update

Yes this is a real Catch-22 invoked by Apple over a year ago, and no matter how many complaints have been received

nothing has been done.

One way to get around it is if you have another Mac or can borrow one, that is running a newer OS, login to the App Store using the Apple ID you use with your 10.8.5 Mountain Lion mac, update your payment details there. Go back to the 10.8.5 Mac and see now if you can update your OS. Or see if you can download one of the newer OS's on the donor Mac. Then make a bootable USB

and then plug that in to the 10.8.5 Mac, boot to the Startup Manager (press and hold option/alt while rebooting), select the USB and press Restart. Once booted to the USB start the installation of the new OS.

How to upgrade to macOS Mojave - Apple Support

How to create a bootable installer for macOS - Apple Support

Hello!

What is model and year of the Mac that you have?

I would recommend that you take a look at the links below and try to upgrade your computer to High Sierra, and if it is compatible to Mojave. This may solve the issue that you are currently facing.

How to upgrade to macOS High Sierra: https://support.apple.com/en-us/HT208969

How to upgrade to macOS Mojave: https://support.apple.com/en-us/HT201475

Let me know if this helps!