After the handle is configured, the select key is invalid. The 6 handles that have been tried are configured to enter the game and will be invalid. Exit the game select button to return to normal.
Which emulator did you run?
I play MAME games. In the game, the select key (on my game pad) is for "Insert Coin", and it works normally. (I configured my game pad via the "Main Menu > Controllers Settings" and mapped the select key to "select".)