Why do some online-portals report only few sales or even no sales at all?
Big online-stores such as iTunes and Amazon often report lower sales than expected. This is mainly due to artists' too high expectations. You have to keep in mind that these shops offer over 35 million tracks, and streaming services and download stores only promote well known artists and labels. All the others disappear in the service's database and can only be found through a specific research. If you or your interpret are still unknown, hardly anyone will look for your song or buy it. Unknown artists can only become famous thanks to their own qualities and to self-promotion.