With the help of @Sorama, we finally solved the problem of order failure, and we are very sorry for the impact it caused.
We guess the specific reason is that the AliExpress platform launched a discount coupon activity, but the discount coupon was invalid, and then the order was closed.
At the same time, the setting of ST42 is that the store discount is only allowed once, resulting in subsequent orders:
1. When using the discount coupon, it will be prompted that the discount coupon is invalid.
2. If the discount coupon is not used, the order will be automatically closed.
It looks like that a problem within AliExpress was triggered, but they did not pay enough attention to it.
In the end, it seems that there is no problem between the buyer and the seller, but the order cannot be completed.
We modify the store discount using times, for those auto cancelled buyer can finish the order on Aliexpress platform now.
Thanks a lot for Sorama and valcher help
We found a bug in AliExpress, it caused us losses, but it seems that we will not get compensation or gifts like Shannon Tweezers :'(