CSACS appliance is not supported in LMS 3.1 as a device to be managed. So, LMS will never "discover" an ACS server. LMS does not manage ACS servers and it therefore doesn't collect any configurations from ACS.
The only thing you can do is put LMS in AAA mode , as you have done, and point it to an ACS server for user authentication and authorisation.
CSMARS can manage ACS servers , but only really through syslog messages received from ACS.
PVV