Teaching a dog to lay down on command can be very difficult. Some dogs just refuse to lay down or just don’t understand what you are trying to get them to do. You have to stay patient. Make sure there are no distractions for your dog. Some dogs do not like to lay down on cold concrete or floors, so maybe put a blanket or bed down for them.
Here Toby took over 20 minutes for me to get him to lay down. I could have easily, pulled his legs from under him or pushed on him. But he would not have learned anything. Being a basset hound means his legs are short and his nose is long. So luring him down and then across the floor, he simply followed with his long nose without ever bending his knees. After 20 minutes, we were successful! He finally laid down. We really did a huge celebration. The next one only took a minute and the ones following were instant.