I bought house in central Oklahoma 4 years ago. It has a plum tree that sits alone in front yard. 2 years ago it produced the best plums I've ever had but none since. I've tried to find out why which brings me here, as I'm hoping to get help identifying it. It's approx 15 feet tall with green leaves, brownish red bark that's got spots and vein-like lines. The leaf stalk is light green. Also the leaves are simple, ovate, with toothed margins not overly sharp.
You said your tree is in your front yard. Is it near or in a lawn? It might be that you've been fertilizing your tree with lawn fertilizer. The high nitrogen for lawns might be suppressing reproductive growth.
Two years ago you had plums. What happened last year? Have you done extensive pruning, fertilized or sprayed with anything...?
Identifying a plum and its variety will be tough. We need to have pictures of buds, leaves, and bark, but mainly the flowers and fruit. Do any of your neighbors have the same tree?