raymondb on "Cannot enable federated logon"

Zen-photo version: 1.4.5, but it hasn't worked in 1.4.4 either.

Running http://my_site_here/zp-core/zp-extensions/federated_logon/Auth/OpenID_detect.php, just redirects to a blank page (http://my_site_here/zp-core/zp-extensions/federated_logon/Auth/OpenID_detect.php?test_query=a%26b).

Nothing in the debug log.

Am I doing something wrong?

Thanks,
Raymond