Subtitles don’t show

I installed and activated this plugin and enabled it to work. Then I added a subtitle for a variable product and for a simple product. On both, the subtitles do not show up. There isn’t much I could have done wrong — unless this conflicts with something else I have installed. Several comments in this support forum state that to get help I should email the dev. but I don’t find any email addres… I guess I should just uninstall and look for another solution.