WeChat mini program login returns 'Application not found for client ID' error

Hello, I am developing a wechat mini program and I am playing around with the example repo. https://github.com/casdoor/casdoor-wechat-miniprogram-example I have modified the code to talk to my hosted casdoor setup and when I make a POST call to https://door.casdoor.com/api/login/oauth/access_token , I get this response from the server :
{
"status": "error",
"msg": "Application not found for client ID: user_n5req9",
"data": null,
"data2": null
}

I've checked everthing looks fine, application, provider, user. Any ideas on why it is returning this message?

user_n5req9 seems to be a user from its name, not an application clientId

I've tried remote debugging on wechat dev tools, I get a 401 error this time. I am posting the client_id as the casdoor application's client ID, I am missing something but I cannot see what it is.