Keychain Can’t be turned on OSX Mavericks

Hello,

I was just given a 2013 MacBook Air by my mom. Before I reset it, it was running High Sierra, and was running fairly slowly. (i5, 4GB ram) When resetting, it was unable to reinstall High Sierra for various reasons, so it installed the original OS on the system: OSX Mavericks. This OS is so much quicker and I really like the UI. 

The only issue is that after logging into iCloud, when I try to turn on keychain, after entering the password, it says: 

“iCloud Keychain could not be turned on. Try setting up iCloud Keychain again.” (See photo)

After this message, I receive a code via text and a notification with a 6 digit code on my phone (as if something to type this in should be appearing on the Mac)

Is there any way around this? Or is it just because the OS is too old? I would really like to use this version if possible. 

If it is not possible, please recommend the next best version of MacOS that I’m able to use that won’t slow the computer down. 

Thank you for any help you can give!