6w5d but no yolk sac or fetal pole

I had an ultrasound yesterday and measured right on time - 6w5d per the gestational sac. It was empty however. No yolk sac, no fetal pole, no heartbeat, etc. My HCG is 36000. Estrogen and progesterone are also within range (and medically managed since I did IVF). They want me to come back in one week to rescan to see if it’s just “behind”, but it seems clearly off to me. Give it to me straight- is this even possibly viable?