If you are persistently seeing a stream down message in the market & API status window, here are a list of possible causes.
1. Betfair is down / has some streaming error.
2. There is an issue with your routing to Betfair.
When these happen, this will affect other users too, so worth checking the forums and here to see if anyone else is affected.
3. There is an issue with your internet connection.
If you are seeing the above on a regular basis, please report the following below.....
A. Which Version of Windows you are using.
B. What Country you are in.
C. Whether you are using a VPN / VPS or Proxy.
...and then turn off streaming.