Your question seems to be a polite question, but it is actually a confident question. Everyone started selling with this mentality.
As far as you are concerned, when there is no movement after ringing the doorbell, you can ring it again; If there is no response, just push the door and go in to see if there is anyone. Some people come for nothing without going in and talking to customers. You will also ask, what if the customer says I came in without knocking? I said so. I couldn't hear clearly whether there was an answer after knocking at the door, so I waited for a while before coming in.