Hi there.

You can totally attempt NEET 2019 again. All candidates can apply for NEET as many times as they want until they meet the upper age limit which 25 years for Unreserved Category and 30 years for Reserved Category. 

For more relevant information click on the following link:

https://medicine.careers360.com/articles/neet-number-of-attempts-and-age-limit

Hope this helps.