You can just simply type the symbol "@" using shift + 2.
If you can't do this, there are some troubleshooting steps that may help:
First is to make sure that the keyboard language is set to United States.
Go to Control Panel then click Region and Language.
Once open, click on Keyboards and Languages then click on Change keyboards and make sure it's set to United States.
If it doesn't work, uninstall/reinstall the Keyboard driver.
Go to Device Manager and uninstall the Keyboard driver then reboot your PC and it should reinstall automatically.
Test it again after the reboot and see if the same problem persists.
If it does, connect an external USB keyboard and if it works, this normally means the problem is the "2" key.
Your last option is to reinstall Windows and if it doesn't work, the only solution would be to replace the entire keyboard.