API Calls from Angular fail on the mobile Safari browser - "Failed to load resource: Preflight response is not successful"

When someone attempts to load the page using Safari mobile, the http calls fails.

Why would a angular http call fail only on Safari?

Here's what I'm seeing in my logs.

Exception type: XMLHttpRequestProgressEvent
Error: 0 Unknown Error
HTTP Result code:   0 
Browser: iOS 15.5 Mobile Safari 15.5

Should be:

HTTP Result code: 200

Debugging details: I tested on a MacBook - connected to a tablet and received the following in the dev tools/network tab: "

"Failed to load resource: Preflight response is not successful"