The app offers you the option to buy a ticket, but you shouldn't do this. You (and every other season ticket holder) should simply check in and out to travel, and if you check in during off-peak hours you'll automatically get the discount.

The Young Person's Day Ticket Off-Peak Hours is for people aged 12 up to and including 18, so you could buy this ticket. It might be cheaper than using your NS Flex season ticket. Note that you may not travel, i.e. be in the train, during peak hours with this ticket. This is different from your season ticket, where checking in during off-peak hours means you may travel with discount during peak hours.

Hey costumer services team

i have have change my subscryption to 40% discount off peakTime 

And the confirmation email was sent to me 2 days ago

but suprisingly the amount of money that calculate for any jurney that i have is the same as previouse and  the travel expense is copelete yet please help me to subscription set on my card 3528050059953853

I can see you have € 14,03 balance on your card, and last used the card today at 9:13

This means the NS Flex subscription is not on your card. Visit a machine (station, supermarket) and choose pick up order.