You will find that periodically your Windows 8 development certificates expire. This is because Microsoft limit the lifetime of these files and you are required to replace them. You'll know when this has happened as your compiler log will advise you of an error building your game and that you need to install a new certificate. Note that when you generate a final certificate ready for publishing your app this is a different system and not covered here - you can find information on this in the section "Create Certificate" at http://help.yoyogames.com/entries/22373488-Submitting-to-Windows-Store
So, how do you generate new certificates? The process is controlled by Visual Studio 2012 for Windows 8, which you should already have installed on your PC.
Inside Visual Studio, simply create a new empty Windows Store application (JS or Native, depending on which certificate you need to replace - you will need to create two projects if you want to replace both JS and Native keys!), let it load the new solution, and then close Visual Studio - if asked, ensure you save your changes.
Browse to the location Visual Studio saved your new solution in (the default location is boxed in red in the screenshot above) and you will see a new certificate has been written out. Feel free to rename it or move it to a new location if you wish.
Inside GameMaker, now open GGS for your project and navigate to Windows 8 > Installation. In here, click the the dots button next to the certificate you need to replace and then browse to the certificate you generated earlier. This will process the certificate and require you to press enter a couple of times. Now click the matching Install button and again confirm the use of the new certificate. It should tell you at the end of the install script that your information has been added. The certificate will then be used for future builds.
At this point you should be fine to build your game again. If you do have any issues on the next build, please try cleaning your asset cache and attempt one more build before retrying these steps.