For 24 hours or so my 1 year old daschund has been out of sorts; very lethargic. Won't eat and doesn't want to go outside for his business or a walk

Could he have eaten/swallowed a ball, toy, inedible object, or human garbage item (tea bag, food wrapper, etc)?
When you say he won't do his business, do you mean just outside or has he not gone at all?
Does he drink water? Are his eyes bloodshot? Are his gums normal color?

Lethargy can be an animal's way of showing pain that isn't evident when they move, such as intestinal, tooth, ear. I of course am just giving ideas.
Twisted bowel is a dog condition that can be very serious, so I would take him to the vet, even if it's just a stomach upset.
When they can't talk, we just don't know.

If these symptoms have persisted for over 24 hours, it's time to consult with your vet. Dogs can go from bad to worse in a matter of hours. Make sure to have water available at all times, it's very important to keep a sick dog hydrated. If you are able, take his temp, a temperature can tell a lot of things.