Sarge won't walk yet either, I thought it was because he's still young... He just wants to hang out in the sun and watch the people walking by. lol.
I'm thinking about training classes at PetSmart for him to open him up a little and see if that helps. I took my Golden Retrievers, Oscar and Emmy (yes like the academy awards...aren't I clever.), and it helped them with walking and being more curious about the world. Hopefully it'll have the same effect on my Sarge. The weigh difference is about 90 lbs, but hopefully the mentality will be the same.