Why can't my devices connect to 5 GHz Wi-Fi?

Hi everyone,

I am facing an issue that I think might be interesting to you. I previously had an iPhone 12 Pro, and I was unable to connect to my home Wi-Fi router on the 5 GHz band. My other home devices connect normally to the 5 GHz Wi-Fi, but my iPhone did not show this network as an option.

Here's an interesting fact: I recently got a new iPhone 15 Pro Max and gave my old 12 Pro to my wife. Now, my wife can connect to the 5 GHz Wi-Fi on the same old phone, while my new iPhone does not show the 5 GHz network for connection.

In conclusion, I believe there is an issue with my account or settings that is preventing me from connecting to the 5 GHz network, but I have no idea what I may have changed. Can someone help me identify and resolve this issue? Thank you!

[Re-Titled by Moderator]