After successfully sending the half-KEY for certification and opening your e-mail program to receive the e-mail with the certified KEY. Detach the file and place it in the directory where the Key was originally created – usually the directory where Board has been installed. Before placing the certified KEY in this directory, make sure that there are no other KEY files in that directory and that the half-KEY has been removed (delete the half-key, don't simply rename it). You can now run Board.
Note:
Some e-mail virus checkers can alter the size of the certified KEY file while scanning incoming messages. This causes the Key file to become unusable. The Key file will not be recognized as being a valid license if its size is different from 1,600 bytes. When you receive your certified KEY file, always verify that the file size is exactly 1600 bytes. Note that it is not sufficient to view the file size in Kbytes because it is a rounded value, you must look at the file properties to know the exact size in bytes.