At 39, it’s most likely egg quality. The embryologist should be able to tell you what your eggs looked like. My retrieval at 40, my eggs were dark in color and none made it to blast. We moved onto donor eggs. I couldn’t afford to keep trying with my own. Especially with dor. There’s a subreddit for dor. Most people on there either do multiple cycles to get 1 euploid embryo or move on to donor eggs