When a new employee logs in for the first time this triggers the Auth0 publisher creating the user in CIS (see mozilla-iam/auth0-deploy#352). This is causing a 500 error in SSO dashboard if this occurs with the user logging in to SSO dashboard.
You can see this in the SSO dashboard logs. It looks like this
The user makes a request during the login to
https://sso.allizom.org/redirect_uri?code=eREDACTEDb&state=4REDACTED4
And the response
HTTP/2 500 Internal Server Error
server: nginx/1.15.10
date: Wed, 02 Dec 2020 15:58:00 GMT
content-type: text/html
content-length: 141
strict-transport-security: max-age=15724800; includeSubDomains
X-Firefox-Spdy: h2
<html>
<head>
<title>Internal Server Error</title>
</head>
<body>
<h1><p>Internal Server Error</p></h1> </body>
</html>