When you select (left click) an object on the canvas, any applicable tokens are selectable from the tokens panel (either by left click or right click to see more specific options). Any tokens that can’t be applied to that object will be disabled, so for example a typography token can’t be applied to a shape.
If you can’t select any tokens, it could be what I think @carolina.portugal suggested above that you have highlighted text inside a text object selected, rather than the text object itself. Or it could be that your text is inside a group or layout, and you have that layer selected rather than the text object.
