iPhone won't sync to computer but iPad will

Perhaps this article will help:

If your computer doesn't recognize your iPhone, iPad, or iPod - Apple Support

Could you elaborate?

Do you mean it isn't syncing or not even seeing it on the computer?

Is the computer MAC or WINDOWS?

Are you running the same iCloud account on all devices?

Have you tried taking off the pin on the phone and connecting it?

Just to make the initial connection...

You've got the iTunes on pc running the same account.