Follow these steps to configure 2FA in DSM6:
Write down the Secret key, it must be specified in the adapter settings. Complete the 2FA setup.
If this do not work out or it can not be found that way (on DSM7 or such) then try this:
Click on "user options" => "personal" => "2FA" => Verification Code (OTP) => Reset devices => "Can't scan it?" and here you get the secret key - copy and paste this to iobroker, go back, scan the code with your mobile and validate it.