My 6 month old female dachshund/chihuahua mix puppy won't pee, how can we encourage her to?

Dogs under stress can hold their waste for an impressively long time. Since she's new to you, it's a good idea to have her checked over by a vet anyway, and this can rule out any medical issues. Other than that, you can try taking her to a variety of surface types (though it sounds like you've probably got this covered with your walks), as she may have a preference for gravel or wood chips rather than grass or dirt. You might also start adding a little lukewarm water to her food to encourage her to drink more. Once she starts peeing more regularly, try to take her back to the same spot and associate a verbal cue with the action, and reward her well whenever she goes in the right place. If she has accidents inside, clean it thoroughly, and move the soiled rags out to your desired potty area to help her make the association.

I think the two answers are above are great. In my experience, dogs (and especially puppies) respond exceptionally well to routine. If you walk your dog regularly and consistently, your puppy will develop natural urges to urinate and the routine will help the dog understand when the appropriate time/place is.

Having a puppy is pretty time-consuming because they require a lot of attention. The habits you reinforce in their early life (from snuggling to up on the furniture to feeding them table scraps to regular walks) will likely stay with them forever. If it were my puppy, I'd try walking him (or her) three or four times a day to try to get a routine down.

there's also puppy aid training spray that you can apply to areas where you want your dog to relieve themselves. a puppy takes between 10-30 minutes after eating before they have to go, from what I hear.