In case you have created your account with Google, Facebook, or Twitch login credentials, you will need to do OAuth verification before withdrawing your funds.
To put it simply, you will just need to re-enter your login data.
That is a security feature to keep your funds safe.
After you enter the address that you want to send your funds to, and the amount, you would need to click on "Re-verify with Google" (if you made an account through your Gmail account):
After that you should see this screen:
Now just choose the crypto, enter the destination address, and the desired amount.
That's it, you should be able to easily withdraw your funds from stake. 😊