How to tell if you’ve been deranked?

Hi All—

I have a product that we put Amazon in October of last year. Since then, we have seen the following sales:

October – 1 unit November – 6 units December – 10 units January – 4 units February – 3 units March – 6 units April – 12 units May – 9 units June – 0 units

Our product is a new, luxury brand in a niche space. We also sell on our own website, and have seen decent sales there this month. As a new seller, I’m worried I broke something on our listing that has lead to decreased sales. We haven’t sold zero units in a given month since launch.

Are there any common causes for this that I should be aware of? Any recent changes on Amazon’s side that might be causing this?