You can’t get refund for unused e-tickets. You can ask money back by delate. On the website you can find how.

If the 4:19 train was cancelled, then the next one was at 5:19 and the expected delay at arrival would have been more than an hour. In such a case, it is very well possible to get a complete refund if you decided not to travel anymore (AVR-NS article 6.3).

NS is not very clear how to apply for such a refund but you could just fill out the form mentioned above, mention that you did not reach your destination and fill in Amsterdam Centraal as the station where you got off.