Did all the resets too..can't get my imac to recognize my iPhone 12 pro max. I got my Macbook pro to recognize it by clicking cds dvds and ipods...but couldn't get the older imac to do it...I'm running El capitan....it says up to date...thank you

Hi there!

Since you're using OS X El Capitan, an older version of macOS, you'll need to use iTunes to sync your iPhone with your Mac: Use iTunes to sync your iPhone, iPad, or iPod with your computer - Apple Support.

If your computer doesn't recognize your iPhone, this Apple Support article should help: If your computer doesn't recognize your iPhone or iPad - Apple Support.

-Jack

The specifications for the iPhone 12 Pro Max say that you can use a Mac that is running macOS El Capitan 10.11.6, in combination with iTunes 12.8 or later, to handle syncing.

iPhone 12 Pro Max - Technical Specifications

You say that you're already running the latest version of El Capitan. So you might want to check that you're running the most recent version of iTunes 12.8 (12.8.2) that's compatible with El Capitan. If you need or want to update your copy of iTunes, you can do it here:

iTunes - Apple

Download iTunes 12.8.3 for Mac (also has a link to the 12.8.2 download for El Capitan)

The iPhone 12 came with a USB-C to Lighting cable.

What cable or adapter are you using to connect the iPhone 12 to the old iMac with USB-A ports?