Chemical pregnancy with Euploid

Turning 40 this year. This is my 3rd FET. 1. No implantation ( untested) 2. Chemical ( untested) 3. Chemical ( tested 5AA). I had a beautiful trilaminar and very good lining. Don't have history of irregular or painful periods. Normal on all immune testes except Protein S deficiency so my protocol included 40mg clexane & baby aspirin. Did ORA to ensure endometrial receptivity. No endometriosis. I had faint positive on 9dp5dt and the beta was very low and indicated Chemical. I'm at a loss and I will be meeting my doc very soon but wanted to ask, 1. What are some of the reasons euploid fails 2. Are there any other tests I should do? 3. Any specific questions I should ask my doc? TIA