There is a problem with the ejector button on these phones. Once it's pressed in too hard or incorrectly it will not spring back up like it should. I'm having the same issue with an S7 Edge. It's likely a faulty or weak design. Hence why putting a stiff item like a cut down credit card springs the ejector button temporarily into place. My advice since the stiffer material springs it. Is to not take the card out any more than needed after getting it sprung back into place. Eventually it won't spring back no matter what you do.