I play games and dislike when games pause while leaving the tab. I have been unable to find a fix for this and I have searched. I use Construct 2 to make these games and if anyone knows of a workaround please message me. Meanwhile, best advice is to play this game in it's own window. If the game is in it's own window I am pretty sure it will keep running.
Can you give us some information about it? Anyway, try another browser.