Are you looking on the website https://www.ov-chipkaart.nl/home-1.htm#/?

If you have an account you can view your travel history. When you select your card, you will see your card details, including the expiry date. The details look like this:

If you haven’t added your card to Mijn OV-chip but have an NS subscription, you can also view the expiry date by going to https://www.ns.nl/selfservice/producten and select Tonen op te halen producten next to your card number.

Hello,

I lost my ov chip card. I wanted to block it. But It’s not linked to my ov chip account and I don’t know the expiry date. I also check my ns subscription to see it. But I couldn’t find it. Could you help me please?

Thank you. 

Customer Service is able to help you blocking it. 030-7515155. It is a 24/7 service. The advices above are helpful though.

Edited my previous reaction because of recent changes to Mijn NS.

A request has already been sent via NS Customer Service to make the expiration date of a card visible again, without having to contact them.

Hello, I lost my personal ov-chipcard and I don’t remember the expiration date. Any idea of how can I block the old one and order a new one??

Contact OV-chipkaart customer service by phone at 0900-0980 (open weekdays from 07.00 to 21.30 and Saturdays, Sundays and holidays from 10.00 to 16.00). They can help you block the card and order a new one.

If there is an NS subscription on the card, you can also contact NS customer service for the expiration date. This can be done by phone; they are available 24/7 at 030-751 51 55. You may also contact them by chat (click the link Chat with NS on this page) or by sending a message on Twitter or Facebook. But NS customer service cannot block your card and help you get a new one.