6 weeks 6 days and couldn’t find heartbeat

Candice • 1 son born May 2020 #pandemicbaby Missed miscarriage and D&C 1-2023

Has anyone experienced this? I had my first appointment yesterday and I was measuring six weeks six days. They could not find a heartbeat and told me to come back next week and also did some bloodwork to check my HCG and progesterone. Has anyone not seen a heartbeat around seven weeks but then seen a heartbeat at eight weeks?