You have a beautiful location there. Spent some time in Chelan; landed my plane once in Penticton, BC.
Your selling difficulty might be one of "exposure". Some realtors have affiliation in large nearby markets in addition to marketing locally. In your case, that might be Seattle, Spokane, Portland, etc. If your agent could do a little marketing of your property in those larger venues, you might land a wealthy individual or family looking to "leave," purchase a 2nd home, or a future retirement site.
I don't plan on selling, but if I ever sell my CA property, it will likely wind up being to a wealthy resident of San Francisco or the Bay Area. Lots of big money floating around there. Less likely a local buyer.