If you are getting an error when logging in that you have an invalid username or password for market data, you should first make sure that you are using the FST credentials that were sent to you from email@example.com. The username will start with "war" followed by a set of numbers, and the password will be something like ab123.
Next, if you have just recently signed up for the simulator access, please note that proper activation can take a few hours (up to 24 hours, but typically less) since the account needs to get set up with the exchanges for live market data. Try signing in again in a couple of hours. In the meantime, make sure you have signed the agreement form for market data.
If you are using the correct credentials and it has been over 24 hours since registration but you are getting this error, please get in touch with our support team by submitting a support ticket. Please provide your FST username so that we can take a look at your account.