There is many reasons why you could certainly fall in Google's index; however, I always start with an analysis on your backlinks. Specifically what Majestic SEO calls "trust flow" and "citation flow". As you can see in the graph you links to the overall domain is light.
Links are still a vital statistic that will show how well you rank organically. You might want to try and find a way to rearrange how your website is inner-linked to your inner pages. This is consider a white-hat-seo tatic to help pass page rank juice throughout your website.
If you want to return, try and create some relationship with bloggers in your niche and maybe offer free products for reviews and have specific links to your inner pages.
The next thing you want to examine is if you have duplicate content. Google duplicate content checker or install screaming frog's free version of their SEO spider to get more data on other SEO factors like:
1.)on page seo
-best practices on your title tag, meta description, meta keywords, keyword density, and how organic of your content.
*biggest deal here is the length on each of these on-page-seo factors. You want 54 characters in your title, meta description about 154 char max and meta keywords 5 to 10 although not a heavy metric or factor anymore. Your keyword density should stay 1 to 3% if you can help it. Just divide the number times you use a keyword phrase by the amount of words for your page.
Hope this helps you get started. See image for Majestic SEO mention.
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