I am pretty new to ISC, so I was just testing disable operation. In Lifecycle state terminated i have selected a particular source under disable accounts. In Identity when I am setting the Identity Lifecycle State to terminated, Nothing is happening i.e. the source account is not getting disabled.
@Amsingh1 Could check the account activity under search for this specific user. If its a disconnected source account, there must be some manual activity required to disable the account, for example a ticket may have been generated if you have an SDIM integration.
Regardless you should see some activity under account activity once the LCS has changed to terminated in the account activity in search.