The Activation Troubleshooter is meant to keep PC users who replace a hard drive or a motherboard from losing their ability to activate Windows 10 on their devices. It also will guide users who may accidentally install the wrong version of Windows 10 to move to the correct version for which they have a digital entitlement.
Testers can try out the troubleshooter by going to Settings > Update & security > Activation and select Troubleshoot.
(In case anyone might be wondering, the troubleshooter doesn't help those not using Genuine copies of Windows to bend the rules and install Windows 10, as Microsoft officials remind testers in today's blog post.)
Update: Microsoft also is adding the ability for users to link their Microsoft Accounts (MSAs) to the activation digital license as of this build. "If you already used an MSA to log in to your activated Windows 10 Home or Pro device, your MSA will be automatically linked. You can use this MSA linked digital license to re-activate your Genuine Windows 10 device by running the Activation troubleshooter, if you run into Activation issues caused by hardware changes."