This is the Frontier Developments Customer Support site.
If you close the verification code window and enter your verification code at a later time the launcher will present the error Invalid Security Code
This is because each individual login will generate a new verification code, if you close the verification code window you will no longer be able to use that code.
If you consistently find that you cannot get past entering the verification code please leave the verification code window open and wait for each previous code to arrive via email. Normally this will only take a few seconds/minutes but in some cases it could take a little while longer. Once you're sure that you have the latest code, enter it into the launcher and it should allow you to proceed.
Please wait... it will take a second!