ID verification code and itunes problems

Hi there. When I try to purchase songs in itunes using my Mac mini, I never get a pop up window to enter a verification code, which I get it on my phone. I haven't been able to buy any itunes for like a year, or more. I can't figure out what is wrong. I used to ALL the time I have thousands of songs. Please help!

*P.S. the device list below only shows Mac mini 2018 or later, Mine is way old like 8 years old. :(