I have an old iPad 3 (on iOS 7.0.4) and I have not used this for a long time, so did not update. If I turn this on, then it asks for iCloud password. I remember the password.
Then one of the two cases occur:
Case 1: If my all other iOS devices are closed, then it does not recognize the password and keep asking for the (correct) password in each 2 seconds.
Case 2: If I turn on my iPhone 7 (iOS 12.2), then in my phone it says something like “another device in ... location is trying to access your account.” There are two choices: Give permission or reject. I guess this is 2FA.
After I give permission to my old device, I get a confirmation code in the iPhone and enter it on my old iPad together with the iCloud password.
It seems to work ( because I see all check marks on the iCloud section of the settings of my iPad) for a couple of minutes. In that time interval, I don’t get any error messages in my devices. But after a few minutes, case 2 repeats over and over again.
At least, I can operate the old iPad without any issue for some minutes but entering the password and confirmation code in each 5 minutes is annoying.
I don’t want to update my iPad because I am not using it actively. Unless there is an easy fix, I consider backing up the iPad and never use it again.
Thanks in advance for your suggestions.
Edit 1: I added iOS versions. I thought that I can not turn off 2FA because on Apple’s webpage it says “if you already use two factor authentication you can no longer turn it off” under the question “Can I turn off two-factor authentication after I’ve turned it on?” in the link https://support.apple.com/en-us/HT204915.
Edit 2: It seems that I partially fixed it. As I said in case 2, I got stuck in an infinite loop: I gave permission to my iPad from my iPhone, got a verification code, entered it in my Ipad, it temporarily resolved the situation, but then the same pop-up message appeared on my iPhone a few minutes after, hence the vicious cycle. To break this cycle, I tried turning off my iPhone 7, then my iPad 3 continued operating normally without any trouble.
I also tried restarting my iPad (keeping the iPhone closed) and strangely, my iPad started recognizing my iCloud passcode too (remember in case 1, I had said that when all my devices were closed I had the trouble with the iCloud code in my iPad, but the iPad 3 confirmed the code now.) But still, when I turned on my iPhone, the same message was appearing continuously in each say 5 (or a few) minutes.