There are a few reasons for this:
1) Your website is less than 1-2 years old. Most domains under 2 years have a DA/PA under 30.
2) You have never built back links to your website and this means you have no other websites giving you their Page & Domain Authority (that's how you get it higher).
3) Your on-page optimization is very weak and thusly your domain is not ranking for anything.
PS: Page Rank no longer has much to do with rankings - it's all about Domain Authority and Page Authority (DA/PA).