Firs of all, welcome to PT (pet talk).

So he's kept outside all day long while you are at work? If so maybe there's something outside that bothers(ed) him? Maybe something happened to him in the past outside before while he was left out there that prevents him from wanting to go out there again for the whole day?

If he's housebroken &/or crate trained is there any reason you can't leave him inside instead? 8 Hours of being indoors or in the crate is not all that bad for them at all. Surprisingly dogs sleep more than some of us might think... I think it's like an average of 13 or 14 hours of sleep a day. They are also pack animals by nature & can sometimes dislike being away from their den & pack members (our home & us, their owners & companions). Give him a kong or two to keep him occupied while you're away.

No matter what the incident was that prevents him from wanting to leave his crate, patience & persistence is the key here.

I would start by keeping him on a lead at all times (and treats on you at all times). When he goes in the crate make sure the end of the lead is outside the crate so you can grab it without entering the crate when its time to get him out. Lure him out slowly but firmly (you are the boss but you don't want to scare him at all). And PRAISE PRAISE PRAISE when he gets out. You can use small treats, favorite toys, petting, etc... all as lures & rewards. Make sure his experience is always good when he leaves his crate. Pay attention to your body language too, especially so if you are feeling frustrated. Remember you must always make this a good experience for him.

If you always get him out at the same time everyday try changing it a little. Follow the above & do it a half hour to an hour earlier or later than your usual time.

Also if you always get him out during a certain routine try to change that as well. Say you put on your shoes & coat right before getting him out try taking him out when your doing something different like eating breakfast or getting your keys ready.

If you taught him a command word to leave his crate change it too. Like instead of saying "out" try "come" etc...

Dogs can be creatures of habit & can really pick on small signals that we often don't see.

Just stay positive, patient & persistent. Good luck!