It means you already have a functional 2FA authorization activated but still it doesn't work from time to time, well it depends on the format you are using if you are using your mobile authenticator where codes get sent to your mobile phone number, note that such otp may get blocked if, your country have regulations against such services.
Best way is to have 2FA application or device where you can generate your codes instead waiting to be sent a code.
So everytime I tried to cashout I had to enter the 2FA code (generated through Google for example) and a SMS verification. I deposited and cashout lots of times but suddenly from one day to another I receive that error when I try to send the sms code and that's why I'm unable to withdraw my money..