Hello, i just got this problem, and i have own solution for this.
1. First of all, check your database at ps_orders (table)
2. Search your order that have a problem with "invalid date", you can search using tab search in phpMyadmin reference to your id order.
2. Then check at invoice_date field. It must be empty, that is the problem, the invoice_date cannot be empty.
3. Edit your invoice_date, fill the date same as date_add field,
4. Save
then refresh your order link at the back end.
done!