This happens mostly when your ordered item is restricted from receiving an online discount. For example Meal Deals, Buy One Get One., etc as they might have been already offered under the discounted price. However, the decision of including/excluding the discount for an item lies with the takeaway owner.
Also, few takeaways will not include delivery charges/service charges while calculating the online discount and just provide a discount for the total value of the items selected.
For Foodhub customers:
Once you enter the delivery postcode it will take to you to list of Takeaways which delivers to your Postcode. You can find the discounts offered by the Takeaway on the right-hand top side of every Takeaway. Terms and conditions will be applicable in food hub orders as well.
In case of any further questions, please contact Live Chat Support on the website.