Coping with two factor authentication

The way that it is supposed to work (and usually does for me) it that the code is supposed to be sent to every trusted device. There is no option to choose a primary device. Occasionally it skips one or more devices for me.

If your iPhone is set as a Trusted device (not just a Trusted phone number) and the code is not being sent to it, you may want to contact Apple Support. There is a Get Support link at the top right of this page. See the information on managing Trusted device and phone numbers in Two-factor authentication for Apple ID - Apple Support

There are many ways to explain this. This is the same info, just presented differently.

A Trusted Device is any Apple device which is signed-in with your AppleID. All trusted devices will receive the 2FA verification code ASSUMING they have a “live” data connection to the internet. (w/o “live” data they won’t know to “pop-up” the special dialog box)

Trusted Devices do NOT receive the codes via SMS.

A Trusted Number is any voice or SMS-capable number(s) you designate to receive 2FA verification codes in the event that you DON’T have access to your Trusted Devices.

They do NOT automatically receive codes; they are sent individually, one-at-a-time to the specific number which you select from your pre-designated list. (After correctly entering your AppleID and Password)

They are effectively “recovery” numbers.

Your actual device generally should NOT be a trusted number. (That would potentially allow fraudsters to receive your 2FA code simply by placing your SIM into their device)

I hope this helps … ???

See also:

Get a verification code and sign in with two-factor authentication - Apple Support

If your iPhone is set as a Trusted device (not just a Trusted phone number) and the code is never being sent to it, you may want to contact Apple Support. There is a Get Support link at the top right of this page.