Why did Apple cancel my order?

You are asking other end users here, not Apple. We can't answer "...why did Apple.." questions.

However, in this matter the cause may be clear. If you are trying to buy from the US Apple Online Store but have a shipping address and billing address outside the US and its territories, that will happen. US Export of Technology laws and other countries' restrictions of what tech their citizens can have determine this policy.

See the section, "Shipping Policies" in this Apple shopping help article:

Shipping & Pickup - Shopping Help - Apple

I'm having the exact same issue, trying to buy the phone from 11 am to 8 pm and still nothing. The only solution they offered me is to go to the store in person, which will require me to wait more than I expected. I'm truly sad that this is my first experiencie with apple, I've never had a problem like this in any purchase ever. Besides, I can't keep re-doing the cetelem process over and over again 😵‍💫

That doesn’t solve the issue and why is this behavior ok? Often times it can be for reasons that are either incorrect or perhaps some other rule the customer is unaware of.

in either event, it’s unprofessional.

That would be unusual. Perhaps you should try purchasing at an Apple Store or authorized reseller instead of online.

I have same problem.

i also keep getting notifications that my order has been canceled