Three possible causes come to mind:
1. Although Flash player is installed, it's not functioning properly. (Go to Control Panel > Programs and Features and uninstall Adobe Flash Player. RESTART YOUR COMPUTER - THAT'S IMPORTANT! Reinstall Flash from here, taking care to deselect the optional offers:
https://get.adobe.com/flashplayer/ )
2. Your security software (Norton, AVG, Avast, McAfee or whatever) is blocking access to the streams. Try temporarily disabling it to see if the problem disappears. (If it does, you'll need to go into the settings for your security software to set an exclusion).
3. The DNS server provided by your ISP isn't connecting to the stream. (Try a different DNS server. See my post here for instructions:
https://www.theanswerbank.co.uk/Technology/Computers/Question1586690.html )