We are just switching from FileMaker Authentication to using Microsoft Azure AD OAuth . Most users are able to log in successfully, but a few users are getting a 502 Bad gateway error in the browser.
Users are running Windows and logging in to with the OAuth credentials set up for FileMaker; they are already logged in when they open FileMaker .
I'm looking for thoughts on why this might be happening and how we might fix it...
Did you have a look into Windows Logs on the computer experiencing the issue ? You may have hints in there.
The generic explanation for this error is:
The HTTP **502 Bad Gateway** [server error response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status#server_error_responses) status code indicates that a server was acting as a gateway or [proxy](https://developer.mozilla.org/en-US/docs/Glossary/Proxy_server) and that it received an invalid response from the upstream server.
The computer where users get this error are they on a different segment of the network ?
Lets call someone who may have suggestions. @Malcolm , did you experience this issue ?
I can't offer much more than you have @planteg. Something misconfigured somewhere. 
These things are meant to work. With luck they all have the same problem, and one fix fixes all. @apjcs I'd be asking IT to look at network rules between those particular clients, fms, and oAuth server.
If some users are able to authenticate and others canโt, Iโd have a look at the security groups in the Azure portal. Are any of those that can connect in the same security group as those that canโt?
If not, then check carefully through the security group of a working account and compare to a group of one that isnโt.
It may also be worth checking the authentication groups within the FileMaker file(s), have they all got the appropriate Azure group Object ID set within them?
Hope some of the above helps.
Regards
Andy