Here is a bit more information to compliment the article that John posted in his first post at the top of this discussion:
Sena Firmware Updater - Sena, the helmet headset manufacturer, is quite diligent about frequently updating the firmware in their devices to fix bugs that users have reported, or to support new developments in Bluetooth technology. Sena provides an application that you install on your computer to load the firmware update into your helmet headset.
You can download the Sena Firmware Updater from Sena's website at this URL:
Sena Device Manager. It is a wee bit tricky to use this application, so, take care to carefully read and follow the instructions presented by the application. You will need to know what model of Sena device you have before you begin - the application is not smart enough to identify what kind of device you have, and the method of connecting and updating varies from one Sena device to another. Sena supplies an online (not downloadable) manual that explains how to use the Device Manager - click this link to read the manual:
Sena Device Manager User Manual. Don't load the software until you have read the manual (don't ask me how I learned this...

)
Updating the firmware usually erases all of the pairing information, which means you will need to re-pair your helmet with whatever device you had it paired with before (phone, GPS, etc.). So, check to see if you have up-to-date firmware before following the procedures that John outlined in his article (post #1).
Generally speaking, you can expect several firmware updates during the first year a new Sena device has been on the market, and perhaps one update during the next two years. If you have a Sena device older than three years, you only need to run the
Device Manager once - after you have confirmed that you have the most recent firmware in your Sena headset, it is very unlikely that further updates will be issued for headsets older than three years.
Strangely, for a company that is as meticulous as Sena is, the third-party Cambridge driver for the Device Manager is not signed (authenticated) in accordance with Microsoft protocols for signing drivers. Hence you will get a warning message when you are installing the program telling you that the driver is not signed. Not much you can do about it except go ahead and install it anyway. By default, Windows 10 security settings don't allow unsigned drivers to be installed, so you may have to make an adjustment to your security settings to tell your computer to "ask" for permission to install an unsigned driver, rather than flat-out refusing to install it. Google
"install unsigned drivers windows 10" to find out what you need to do.
Garmin's Headset Compatibility List & Video - Garmin has compiled a (partial) list of headsets known to be compatible with the Zumo 590 / 595 devices, and has produced a small video describing the pairing process. This information is available here:
Bluetooth Headset Compatibility for zumo 590 and 595
Michael