Unable to single sign-on with Nagios / Thruk

[stwongst]

Hi all,

We're new to Nagios + Nagvis. Installed a basic configuration:

Rocky Linux 8.7
Nagios 4.5.0
Nagvis 1.9.40

Added link to Nagvis in Nagios side bar.
We didn't change Nagvis' httpd conf, leave basic authentication setting commented out.

In /etc/httpd/conf.d/nagvis.conf:

#AuthName "NagVis Access"
#AuthType Basic
#AuthUserFile /usr/local/nagios/etc/htpasswd.users
#Require valid-user

In nagvis.ini.php:

[global]
logonmodule="LogonMixed"
logonenvvar="REMOTE_USER"

User nagiosadmin is created in Nagvis user database with read only right.

We always see the Nagvis login page when clicking the link added to Nagios.
Checked the $_SERVER[REMOTE_USER] is defined under path /nagios, while it is undefined if I check that again in paths outside /nagios.

Did I miss anything?

Tried the integration with Thruk and also failed.

Sorry for the newbie question.
Please help.
Thanks and Regards