Invalid signature in request credentials

Is there any updated documentation for setting up the Authentication? I know it has to be close because the username is the integration key. If I put in incorrect integration key, I get an error for that.
When using correct integration key, I get the subject error.

Duo Auth API | Duo Security

Hi Henry,
Are your parameters listed in alphabetical order? That is one of the most common reasons I see this error occur for people.
From this help article on API error response messages:

40103 Invalid signature in request credentials indicates that the signature is formatted incorrectly.
To resolve this, you should verify that the signature is encoded in hexadecimal ASCII; is using the correct HMAC-SHA1 signature as the password; and lists the parameters in alphabetical order.
If you receive this error while making calls with PowerShell or C#, please see this article.

There have been a few community posts on this in the past, so I will try to dig those up and see if they include any other helpful info I’ve missed here.