Hearthstone legend says that when Battle.net can't log in, gray can't be clicked.

Refreshing your IP address and DNS cache usually helps solve connection problems.

For Windows:

1. Click Start, and then click Run.

2. Enter cmd in the run box, and then press Enter (a command console window should appear).

3. In the command console window, enter ipconfig /release, and then press Enter.

4. Wait a few seconds and get a response that the IP address is released.

5. In the command console window, enter ipconfig /renew, and then press Enter.

6. Wait a few seconds to get a response that the IP address has been re-established.

7. In the command console window, enter ipconfig /flushdns, and then press Enter.

8. Close the command console window and try to play the game.

If you are using Windows Vista, you will need another way to load the command console:

Click Start, select Programs, select Accessories, find Command Prompt, and right-click Command Prompt.

Select Run as Administrator from the drop-down menu.

Then start from the above Windows operation until step 3.