Convert to video timeline

At the moment, when I open the timeline, the only option seems to be the one in the centre, to convert to frame animation, and the three dots on the bottom left (where the option was to convert to frames previously) is inoperable (Photoshop won't allow me to click on it). I can then convert to frames and edit, but when I try to convert to video timeline in order to sharpen and colour, the option to do so (in the same place as the three dots) is also not working. Does anyone have any idea of what has gone wrong? Have updated my Photoshop, etc., and can't see anything visibly wrong.
