On this page, you will find more information about the most common causes and most relevant solutions for the WeChat error '40001'. Do you need help straight away? Visit our support page.
The WeChat documentation indicates that error code '40001' is caused by the following problem: "Unable to get access_token due to incorrect AppSecret, or access_token is invalid.".
Do you think there is another cause for this error? Let others know in the comments.