There are different methods to find out if your website is penalized or not. Some of them are mentioned below.
1. Go to Google webmaster tool and check if you have received any warning message. If yes then you are penalized.
2. Check your traffic flow in Google Analytic. If there’s a sharp drop in traffic flow, then this is a clear indicator of a possible penalty.
3. Go to Google and type in site:yourdomain.com to check whether your site is still Indexed or not.
4. Or you can search your website without using ‘www.’ or ‘.com’ extensions. If the site still appears on search engine results then the site is not penalized nor banned from Google.
To avoid these penalties you need to be current regarding the Google update and SEO techniques.