No sensors displayed in webUI

[Max Power]

Hi

What are the basic requirements for phosphor-webui to display the list
the available sensors?

I've create a simple entity-manager configuration for my custom hardware
containing some voltage and temp sensors definitions. All the configured
sensors are accessible under "/sys/class/hwmon/hwmon*".
"entity-manager" and "dbus-sensors" related services like "ADCSensor" or
"CPUSensor" are up and running, "busctl tree" lists all the sensors
under "/xyz/openbmc_project/sensors" and I'm able to read the sensors
properities using "busctl introspect".

But the server-health/sensors-overview page in webUI always shows 
"There are no sensors found."

Any hints or ideas what I am missing?
Do I need any other services running besides "entity-manger" and
"dbus-sensors"?

Max