The current hints on recommended software and hardware as well as network configuration can be found in the linked FAQ article Requirements.
If problems occur when using BigBlueButton you can check the following points which are explained in more detail below:
Low bandwidth can lead to problems with the transmission of audio and video. In this case check your internet connection and, if necessary, reduce the load by background activities of your device or other devices in your network. For more information see the FAQ article Requirements.
If the session is opened in a non-recommended or outdated web browser, errors may occur. In generel, it is always recommended to test another browser in case of problems.
Ad blockers, which are partially integrated in popular web browsers, can also cause problems. In this case check the settings of your browser or ad blocker for an option that allows you to share your local IP address with WebRTC.
Problems often occur when the transmission of audio or video data is blocked. BigBlueButton then displays an error message in form of "Error 10xx". Such a blockage can occur due to firewall rules in the network of the organizational unit, in the home router or computer.
If you use a VPN connection, it may have its own firewall rules and be the cause of the error. If possible, switch it off if a problem occurs or contact the administrators if necessary.
One possible solution besides the correct firewall configuration is the use of OpenVPN. If it has to happen very quickly, switching to another device that is not on the same network, e.g. a smartphone with a mobile data connection, usually helps.
An anonymous test room from the the BigBlueButton instance of the TU Dresden is available for external users to check all functions and especially the audio and video connections. For the test of the microphone, in contrast to all other BigBlueButton conferences at the TU Dresden, the echo test is directly accessible there.
For a complete error analysis, a function test on the test server of the BBB developers is recommended. If problems occur here as well, this indicates a fundamental blockage of necessary network connections. Otherwise it indicates problems with the accessibility of the BBB servers at the TU Dresden.