The Nintendo Switch Online version of StarTropics is lacking a code necessary to make progress.
It's tempting to believe that the problem lies with the digital conversion of the game. StarTropics is an interesting case - when it originally launched, its instruction manual contained clues which were necessary for the player to make progress at certain points. One of these is a letter to the protagonist Mike from Dr. Jones. Players needed to immerse the letter in water in order to reveal extra instructions which were needed to make it through StarTropics' fourth chapter. Obviously, this isn't possible in the digital version of the game.
The odd thing is that this issue was already solved by the Wii U version of StarTropics. In that virtual console release, the letter - complete with extra information revealed at the end - was available at the very end of the game's e-manual (the digital instruction manual accessed through the Wii U's menu). The Nintendo Switch Online version of the game doesn't have this letter included anywhere, making it hard for players to progress. We live in the wonderful age of the Internet, so you could just search for it online, but hey, where's the fun in that?
That said, there isn't much fun in being stuck for ages if you are trying a blind playthrough of the game. For those who are well and truly without recourse, here's the letter in its entirety:
StarTropics was released alongside Kid Icarus for the Nintendo Switch Online subscription service on March 14th. The two games are available for Switch Online subscribers to download right now. Normally we'd advocate playing games with as little outside help as possible, but this is one area where it's safe to consult the Internet for help.
Did the lack of Dr. Jones' letter flummox you? Have you already played the Wii U version (or do you own the original NES game)? Let us know in the comments below!