Cannot key in verification code on old iPhone

I have an old iPhone 4 that is not regularly used. Recently I have been trying to update some apps on it, but I cannot figure out a way to login to my Apple ID on the phone.

After typing in the password for the Apple ID, an error message would appear saying that an Apple ID verification code is required to sign in, and that I have to enter the code shown on my other devices after typing in the password.

Here's the problem - I have tried allowing access for this old phone on both my current iPhone and Macbook. Yes, I received 6 digit verification codes whenever I do so. BUT, nothing pops up on my old phone asking for the verification code? How in the world am I supposed to go about keying that in...?

Please helpppp...