7+5 weeks No Heartbeat

Ca

So we had our first visit this morning and there was no heartbeat and we were measuring between 6&7 weeks. Next dr appointment is in 2 weeks for a viability scan. What are my chances for the heart to start beating? Has anyone else had this and gone back for everything to be okay? I’m preparing for the worst but would like to know if anyone has had something similar and everything work our fine.