Missing good in order - no response from Help centre

I placed an order on 15/01/2022 - the order was delivered one item short. I checked my invoice on the app - and item should have been included. I then e-mailed help@sixty60 and received an automated response. I waited 2 days and still no response - I e-mailed once again (as the call centre number does not go through). And still no response. This has been very disappointing. Mistakes can happen - but just giving a customer feedback is the least that one expects.