I have occasionally had this problem both with the store and when checking for updates. I have found that if I reboot everything works again. When I say reboot I mean holding the top button down until the tablet is actually off, then pressing it again to turn it back on. The tablet should display the SURFACE logo when turned back on. I don't mean to say that everyone who reads this dosen't know how to turn thier tablet on and off, but when I told my daughter to do this, she didn't hold the botton down long enough and only put her tablet to sleep, which will not fix this problem.