I’m trying to access my trello cards programmatically, but all the documentation I see references an API Key and a Token,
I’ve generated the API Token in my Atlassian account (can’t see the option in trello) and when I try to use this key to generate a token I get a 404 response.
You have to generate the API Key in the Power-Up admin portal:
Even if you are not creating a Power-Up, you will need to create a “Power-Up” as a placeholder for your API key, apply a logo and information to it so that when the user signs in and approved your integration you they will see your information and logo. Anyway, on the Power-Up options you will see the second option on the panel is “API Key.” You will generate one of these and use that in your integration calls.