Hi,
The situation is strange even before that.
Normally, HikaShop will create an invoice number for an order when the status of the order goes from "created" to "confirmed", which normally means that the payment has been received by the payment gateway.
I can see that the status of all your orders is "created". So actually, the current situation with the invoice number looks normal to me and the problem is more about why the status is not changed to "confirmed" after the payment ?
Now, what controls the invoice number generation is the "invoice" column under the System>Order statuses. By default only the "confirmed" and "shipped" statuses are enabled under that column. Since the invoice number was generated before, even though the order was created, I suppose this all means that you had the "created" status enabled under that "invoice" column in the past, and you disabled it on the 24th.
So please check that.