The error message 1004 is likely caused by security extensions in your web browser. For example, the error message could be triggered by Privacy Badger, NoScript, AdBlock, or similar extensions. Many of these extensions are available for all major web browsers.
Make sure that none of these extensions are preventing BigBlueButton from working. For example, in the browser menu (in this case, Firefox), you can go to “Settings” and then to the “Privacy & Security” section to specify whether pop-up windows should be blocked and which page elements should be blocked.