@TappingTed to start with we did just let her cry for a while, no more than 10 minutes, and then the second she was quiet we took her out just in case she was desperate for the loo, which a couple of times she was. But then we put her back in and she just settled down. I then go off and do things with the tv or radio down lowish and give her at least an hour. I think looking at how they are behaving is a good guide to when they should go in there. When extreme landsharking starts happening in she goes. If she is trying to find a corner to sleep, but keeps getting up and is generally unsettled, I pop her in.
At night, after I take her out for a wee, I then pop her on the sofa with me until she settles back down and then I put her back in the crate. I'm hoping I will just be able to pop her straight back in, but I think I mentioned before I am very conscious of disturbing my dd who sleeps downstairs so don't want Rosie crying and howling
I tried treats in there, but that didn't really help. She has a couple of toys that the breeder gave her, and sleeps on some vet bedding and the crate is covered so it's nice and dark in there.
I don't know if any of that is of help, but I think trust that he is safe. Obviously check if he sounds too distressed but don't leap to let him out as soon as he makes a noise. Rosie does this but she settle back down quite quickly. Quite often she is just sat there looking so I try not to make eye contact.
There are other ways I've seen that can help, but they take time. You need to build up him spending time in there with the door open, having treats, playing with toys so they feel comfortable.
Good luck!