I have 1.5.0 and have been a long time user of Jaksta on Mac 10.11.5. Unfortunately this version seems to NOT work just about anywhere. Youtube? Nope. Vevo? Nope. Major porn sites? Nope. Music from Spotify? Nope. Vimeo? Nope. Pretty much anywhere I try it doesn't even detect a video or audio stream.
Can you send us the log file? You can find it by going to the Jaksta Preferences and clicking the Find Log File button.
Jaksta should work on most of those sites (and does for me when I test it here). There is a known issue with Spotify at the moment.