If the Windows Store doesn't open when you tap or click Store on the Start screen, try running the Apps troubleshooter. This tool can automatically identify and fix some problems with the Windows Store. It's only available in English, but will work on PCs running any language.
If you can open the Store, but are having problems signing in, check to make sure you entered the correct Microsoft account and password. If the info is correct, but you're still having problems, you might need to reset your password:
Go to the Reset your password website.
Choose the option that matches the problem you're having, and then follow the instructions on the screen.
Choose how you want to reset your password, and then follow the instructions.
After you've reset your password, it's a good idea to add as much security info as you can to help make your account more secure. If you forget your password, or if someone else tries to take over your account, you can use this info to get your account back.
If you can use your Microsoft account to sign in to other apps or services, you can try clearing the cache for the Windows Store on your PC.
Swipe in from the right edge of the screen, and then tap Search.(If you're using a mouse, point to the upper-right corner of the screen, move the mouse pointer down, and then click Search.)
Enter run in the search box, and then tap or click Run.
Enter wsreset.exe in the Run command and then tap or click OK.
The Windows Store will open after the cache has been cleared.