I'd start by taking a look at your link profile. I did a quick check with Moz and Majestic SEO and noticed a couple of things:
- You have very few incoming links (0 recorded on Moz, 84 on Majestic).
- None of the Majestic inventoried links have any citation or trust flow, meaning they're considered very low quality.
- The majority of the Majestic inventoried links are tagged as having been deleted.
Another quick note (but this wouldn't prevent you from being indexed) is your tag pages are indexed. I'd change those to noindex to minimize duplicate content.