You need to update the changed password in DBCO for that SLT configuration. After updating the password in DBCO, test the connection using the report ADBC_TEST_CONNECTION.
I dont think there is a default password for the user created automatically by SLT configuration, it generates with some random password, which we would not know. What I do generally is, as soon as the user is created by SLT configuration, I change the password and update it in DBCO for that configuration.