iphone 12 only gets 90$ trade-in value with premium unlimited account

Hi,

I was told that I can upgrade my phone with great trade-in value with premium unlimited account. So I signed it up around 1.5 month ago. However, when I try to order the new iphone 17 these days, the website shows the trade-in value is only 90$, far below the threshold 500$, even though my phone is in a great condition (i.e. answered 'yes' to all the trade-in question).

Does anyone know why? Thank you.