Adobe flash player auto. installed on windows 10 but says couldn't load plugin

trying to upload and send invoics thru yahoo. mail at but message goes through but no downloads.  Then i go to the site where these inv. are supposedly sent bu theres nothing received.  That's wher it finally comes up saying couldn't load plugin.  Shockwave flash says it's unavailable.  So now i'm totally confused and to boot, i am not all that computer savvy.  HELP