Quick way to eliminate cookies as a problem, install another browser you won't use regularly or just test with IE if you don't use that and try again with a different browser.
If it works then go back to the one you were using and clear out the temp files & cookies
Don't think it's that Rich, it was only vine videos that told me I needed to download an app, I have not downloaded anything but I can now watch vine vids with no problem!
