Sync button not working on a Big Jambox

My beloved Big Jambox is only synced to two of my devices and now the button behind the soft outer button has seemingly disappeared. I removed the side panel and nothing is there and so I don’t know what I’m missing! Can anyone help me? What is meant to be there? There doesn’t appear to be anything loose inside. I love this speaker and would to be able to sync it once again with my modern-day devices… please help!