Unable to get verification code for Apple ID

Apple TV won't let me log in using my Apple ID so I tried to log into my Apple ID using my computer to try to see what the issue is.

When using my computer, Apple ID lets me log in partly then asks me for a verification code. I requested a verification code be sent to my email address but the code never arrived. I tried this again many times. Still no code arrived. My email address is definitely correct and it's the one I use as my Apple ID. After many attempts over several hours I got the message "A new code cannot be sent at this time. Please enter the last code you received, or try again later." I haven't received a code so I cannot use the last one that was sent to me!

Next, I decided to try re-setting my Apple ID password to see whether that would fix the problem. I succeeded in changing my password, but when I try to log in I get the message "A new code cannot be sent at this time. Please enter the last code you received, or try again later." I haven't received a code so I cannot use the last one that was sent to me!

I've had the same problem countless times in the past months and years trying to log into my Apple ID when using iTunes. I now have an Apple TV 4K box and subscription, obtained as part of my Vodafone broadband contract, that I'm unable to use.

Why are the verification codes not being sent to my email address? Having verified my account in the past, why am I having to verify it again?