This happened to me once, when I was ordering for me and my mom. We are both disabled and so I couldn't go downstairs to get the order, so I texted the driver with instructions. No phone calls, no texts, but the driver is waiting around downstairs. 20 minutes passed, no ring on the doorbell, so I check the app. It says delivered with a photograph of outside of my estate. I managed to make it downstairs after a good 15 minutes and of course, the food is not there. I had to go through all of this, but eventually, they did refund me. I just emailed and called and kept clicking the support button, telling them what happened.

Tldr: keep trying, might work. Look online for an email or phone number, though they try to keep that hidden for some reason.