If it's a paperback, those don't show until shipped.
If it's an e-book, your customers may be fibbing to you, just to get you off their backs (happens more often than you think). E-book Orders show generally within minutes to hours. Those convert to sales (assuming the payment goes throught) in minutes to days .
Rarely, a sales no-show will be a reporting glitch. Possible and not unknown, but doubtful.
I suspect there are issues at the moment.
I ordered some of my own paperbacks for friends - they have arrived and are not recorded.
Also I am near the top of ratings (moving up a number of places in last few hours) without sales in UK and US.
I am sure Amazon will let people know if there are longer term problems.