Can not place an order with the education discount

Hi! So this is the issue that I am facing:

I ordered an iPad Air few days ago with the education discount, but I returned it. Then I reordered an iPad pro using the education discount, but I realized I ordered the wrong one, so I canceled it within 30 minutes, plus, I hadn't paid for it at that point. After that, I purchased it again with the education discount and it said: Your order cannot be processed. you have exceeded the product quantity limit for an item in your bag.

I don't know why this is happening since I didn't even pay anything. After talk with apple support thousands of time, a customer service agent emailed Apple for me today, and then I received a reply from Apple E-Purchase Orders saying: We've determined that the quantity of items in your order does not exceed our maximum per customer. You have 24 hours from the time this email was sent to place a new order.

But I tried it again and again, still doesn’t work.

Also I want to use my Apple account balance on this, so I have to use my own Apple ID to place the order.

Does anyone have the same experience or know how to deal with it? I have spent on the phone with apple support at least 7 hours and my issues still cannot be solved. This is SO FRUSTRATING and I am SO DISAPPOINTED in Apple support...