I don't have a complete walkthrough, but reply with where you are in the game and what items you've found and I'll give you some hints :)
Viewing post in Legend of Etad (for Playdate) comments
Itch still somehow doesn't have spoiler markup for comments, so I made a gist with graded hints.
I'm assuming this is the key you're missing, but let me know if it is a different one.
Oh no! That certainly is something I hadn't thought of.
I'll need some time to patch this, but I can fix it for you right away if you are able to send the `playerstate.json` file from the save folder (via data disk mode) to gareth@garethw.net
OR, if you're comfortable editing json, simply change "position" (near the bottom of the file, with only one indent) from "x":21 to "x":18 in the playerstate.json file
Huh. That's concerning.
Did you put the first three keys in the door before looking for the 4th?
If so, sounds like your save got corrupted somehow.
You can fix it yourself by editing mapstate-9.json, search for "hasKeys" and change it to 4.
Or send mapstate-9.json and playerstate.json to gareth@garethw.net