You would only see the convert cache button on a site set up with an older version of Maps that hasn't yet been converted; you wouldn't see it on a newer site or a site where that button had already been pressed.
For your current site you can check in phpMyAdmin whether it has the table wp_toolset_maps_address_cache and whether it has any content (cached addresses).
If you don't see the table and don't see the button then I may have got that wrong, let me know and I'll investigate further.