I cannot able to add card in one of the board list. How to add card?

[Fatima Sultan]

in the first image, upon clicking add card, it will disappear and card is not added. 

[Rasmus Wulff Jensen]

Have the "Collection" card been added to the board via a PowerUp or Code? If so you are properly hitting this bug: https://jira.atlassian.com/browse/TRELLO-779

To temporarily resolve the issue, move the "collection" card to another list and the back to the original list, then the add button should begin working again

To permanently resolve contact the individual who made the card via code and request that they use pos=top instead of pos=0