One reason agents may miss chats is because of their Auto-Away setting.  This feature will automatically put agents in away-mode after a default idle time of five (5) minutes.  The Velaro Agent Desktop does this to insure if agents step away, take a call, or are otherwise preoccupied, they are not being sent chats.  However, you can set the auto-away to zero (0).  This means agents will never be automatically set to away.  Then the agents can manually set their away status in the drop down of the Velaro Agent Desktop.

Here are the steps your agents need to take inside the Velaro Agent Desktop:

Tools > Options > Autos (middle of screen): Open up the Autos display (click the + sign)

Look for:

Auto-away after:

Make sure it is set to 0 minutes (default is usually 5 minutes.)  Hit apply, and then OK.