If you are seeking new features, the most effective "update" is upgrading to the JBL Go 4 , which addresses many of the Go 3's limitations:

Press and hold the and Bluetooth buttons for about 5 seconds.

Are you experiencing a like Bluetooth disconnecting, or are you just looking to see if new features have been added?

JBL typically ships this model with a final, stable firmware version. Because it lacks complex features like PartyBoost or Wi-Fi, there is rarely a need for post-launch bug fixes.