most likely an issue at Operating System level.. see other threads on same issue
on the other hand, did you use FB's /live/preview portal, confirm stream key (maybe create new one?), etc? Have you tried a schedule stream, and done the connect in advance and see stream in FB's Preview window? if not, what are the FB alerts/logs indicating?
side observations
- not specifically your cause, but you source check your OBS Studio log. that audio device enumeration error... a good idea to resolve that (possibly at Operating System level, disable unused devices... remove from OBS Studio at Global level if never going to use.. etc)
- streamelements highly correlated with problems. I've seen it cause network issues with all its timeouts. I've never learned whether issues caused by poor (immature/unreliable) software coding at StreamElements, or if a user config issue
