Help with crate training

Hello, my puppy is a 15 weeks staffy/mastiff and he's currently doing really well with training. However, we are struggling massively when getting him to settle for naps in his crate and in his crate at bedtime. He had been doing well as we were putting our hand in whenever he was quiet, covering his crate and playing white noise. He would cry for around 5-10 minutes until he settled himself and would sleep for hours. If we weren't in the room he would cry as he realised he was alone, then we would only enter when he was quiet to settle him again. He also used to sleep throughout the night in his crate, only waking up at around 5am to go outside.

Then we went on holiday for a week (with a solid schedule so we thought he would be great), leaving him with my parents and they completely abandoned the crate and let him up on the bed. After we came back, there was a heatwave and he was extremely uncomfortable in his crate and he had to sleep with us. Now his crate training is going really badly and he struggles to settle in there without howling/screaming for us even when we are right there.

We have tried doing less play before nap time and giving him lickmats before naps and bedtime but he still cries and will not settle. Then because we can't enforce a nap he will just stay up until he is overtired and starts biting. We are feeding him in there and dropping treats for him to find and he just seems to hate it. The only times he settles in there without crying is when its been a couple hours of him chewing/licking at something then he sleeps without issue. Should we just enforce his nap earlier and then he has a long time to calm down and self soothe? Any help is appreciated or suggestions for how you settle down your pups for bed as I feel like I've tried everything for him and can't get him into a routine where he understands its bedtime.

We are also in a temporary living situation with my parents and don't have space for a play pen. We have had a stressful couple months with him due to changes in circumstances but he is settled in every other aspect of his life now aside from sleep.

I should also add we have had him since around 8 weeks, as his mother was lashing out at the puppies and the breeder asked us to take him sooner. So he has been attached to us since a very young age, but he does well when left on his own with other people.

Thank you for any advice!