If you can hear the audio but cannot see the video, you may be experiencing issues due to browser hardware acceleration and its incompatibility with certain graphic cards. Try disabling hardware acceleration in your browser:
1. Open a new tab and go to "chrome://flags"
2. Find "Disable hardware-accelerated video decode" and click "Enable"
3. Restart Chrome
1. Click the Firefox button at the top-right of the Menu bar
2. Go to the "Options" menu and then click "Options" again
3. Click the "Advanced" tab at the top, then "General" below that
4. Uncheck "Use hardware acceleration when available"
5. Click OK and restart Firefox
1. Click the Settings (gear) icon
2. Choose Internet Options
3. Select the Advanced tab
4. Check the box under Accelerated Graphics that reads "Use software rendering instead of GPU rendering"
5. Click Apply, then click OK
6. Restart Internet Explorer 11