If @sjaakie 's suggestion of clearing the filters and search box do not fix yur problem it is likely that you have accidently used the "hide" option for one or more of your cards (clicking on the crossed out eye icon on the card on its details page will do this).
To unhide cards go to your "My Collection" page, clck on the icon that looks like three horizontal lines with small circles on them, open the view sub-menu in the menu that will have then appeared and select "hidden cards". From there you can unhide individual cards.
(As the original poster's location is given as France it might be helpful if a French speaker could provide a detailed explanation of how to unhide cards)