Why is no one buying my in-app purchase ?

Today i got over 3000 downloads. Only one bought my in-app purchase. People can't really do much with the app without buying the Pro Version. How is it possible that out of 3000 people only one is willing to pay for the pro version ?. My Pro Version is only 0.99 $... . It does not make sense at all. Let's say 1.000.000 people download my app. Do i really make only 300 $ from that ?
Btw my app is in the category productivity. You can create PDF's and write on it. It is like GoodNotes or Notability. My Pro Version has features like handwriting recogition, unique templates, insert text and images, scan documents and more.
Why is no one buying my in-app purchase ?
 
 
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