This is a new Dell laptop with latest updates of Window 10 and Firefox 75.0 (64-bit) . Last laptop did not have this problem. When I try to open a Youtube video, this is the error message. "The address wasn't understood. Firefox doesn't know how to open this address, because one of the following protocols (rtsp) isn't associated with any program or is not allowed in this context. You might need to install other software to open this address." How can I resolve this, please?