Since SEO consists of around 200 different variables, there are many things you could be doing wrong and there are many things you could be doing better.
While taking a look at your site, I found a handful of things that jumped out at me.
- You Blog Titles are H5 tags - **This is a problem - **Google looks for an H1 tag to identify what the article is about. Its good that you have a blog on the site as it will aid your efforts in getting organic search traffic. You need to optimize the blogs to target the keywords that your intended site visitors would type into the search bar. Like - 3d model blueprint, 3d printers, purchase 3d designs, sell 3d designs, and more. Try to put your most highly valued keyword first as the keywords are given weight by their order, first - most valuable and last - least vauavle.
- Use more H1 - H5 tags to create a hierarchy for your articles which will help your SEO
- Use more images in your articles, with appropriate alt tags and optimized meta data (filename, alt tag, descrition, captions)
- Create more interlinking structure from your blog to your products pages, and to other blog articles on your site, do this while using semantically relevant alt text which will aid search engines in associating your domain with other semantic concepts.
- Think about implementing schema.org, open graph protocol, twitter cards, and microformats. This will increase the semantic understanding of Google's bot crawlers.
- Check the Search Council for Crawl Errors, I tried to crawl your site but got denied, you might be doing this to Google's bots. I used Screaming Frog SEO but the site wouldn't respond, maybe this is by design, just wanted to bring it to your attention
Email me at larionovdmitri@learninternetgrow.com if you want to schedule a time to have a more in depth discussion.