Can I request the cancellation and refund of the money?

 
A thousand days ago I made the purchase of an EA but as of today the provider has not shown interest in helping me clarify some doubts about the installation. Can I request the cancellation and refund of the money?
 

Officially from MQL5.com no, you will need to contact the author/seller for that.

In any other case you can contact the Service Desk at the bottom of this website.