Please clear the cache and browsing history on browswer being used.
Clear Cache - Click Here
You may also try a different browser to see if that resolves the issue. If the problem persists, your internet connection may be experiencing network congestion.
Is your technology ready? - Click Here
System Requirements - Click Here
Audio Issues? First check that...
A) Your computer supports sound
B) Your computer's speakers (if external) are turned on
C) The system's audio level is turned on at a high enough level