Hi,
Here’s the [https://fccid.io/APIONYXST2/User-Manual/UserManual-pdf-2536792|manual] for the speaker. (if you can call it a manual that is). It doesn’t mention anything about resetting the speaker
Here’s a [https://www.harmankardon.com.au/support-knowledgebase.html#onyx%20studio%202%20reset|link] that shows how to reset the speaker, which may not be the same as a factory reset. You can only try.
FYI there is no firmware publicly available for the speaker. If the firmware needs to be reinstalled or upgraded the speaker has to be returned to the manufacturer. Also not too helpful