Confluence DC has a problem when connecting via Ivanti Connect Secure

[Jim Knepley - ReleaseTEAM]

I've got a Confluence DC cluster working pretty well, unless someone connects to it via Ivanti Connect Secure, which is a TLS VPN. More or less a glorified reverse proxy.

Through Ivanti, Confluence responds to the login.action page with this message decorated with a big red triangle with an exclamation point: "Something went wrong and we couldn't load this page. If this issue persists, contact your admin."

Well, I'm that admin.

There are no relevant server logs to speak of; the only hint I see is part of the URL, which includes a GET parameter of "permissionViolation=true"

Chrome devtools aren't very revealing since they only show communication with the Ivanti server, but nothing looks particularly out of place.

Jira's working fine, and the error appears to be generated by Confluence, so I think we're fine from a networking standpoint.

Any troubleshooting suggestions would be appreciated.