It shuld work, it might be a filter problem however as most florecent microscopes have 547 nm red filter  with Alexa Fluor 647 exitation range is between 594-633 nm. If you have 594 red filter in your microscope you shuld try this one out. You don't need any sample just put 0.5 ul of antibody solution to the slide glass and try to see if it glows.