What is this pop-up and how do I stop it?

[F0REVERY0UNG-]

I get this pop-up on my phone every single day. Every time I get it, I approve it on my MBP, but it still comes back either later in the day or the next day. What does this even mean, and how do I stop it for good?

Sent from my iPhone using Tapatalk

 

[BreakingKayfabe]

If you don't use iCloud Keychain then go into Settings-iCloud and turn off Keychain.

 

[kch50428]

Click on one of the choices... go to the other device and get the code, or click the other choice, and approve with your previously set up Keychain security code.