2017 Mazda CX five had Apple CarPlay installed at the dealer when I bought the car three years ago now when I plugged the cord into the USB that's designated for the Apple CarPlay it doesn't work but when I use the other USB that's for charging it works so I don't think it's the cable. I'm at a loss.

 

Sounds like they hooked the cables up incorrectly.

 

He said it was done 3yrs ago. I assume that means it was working properly and suddenly the connection reversed. That is quite strange - unless they did additional work recently.

 

You know what they say about "assume." He may never have paid attention as to which port he was using.

 

Lol...

 

As others have posted.
How do you know for sure which is which, are they labeled?
Unless you've had other work done the inputs do not "miraculously" change by themselves.
And as you say, it works with the "charging" USB, meaning if it works with that, exactly what is your issue?
You can use a USB device while it is charging.

 

I know it's only one out of 2 USB ports on those pre-2021 models that allows the CarPlay connection. It's the top port and should look similiar to the photo below.

 

My 2020 has navigation and my phone connects via Bluetooth.
I use an old phone as a music player and use an audio out cable to the auxiliary in which works far better than USB or Bluetooth.