Provided after successful installation; Net8 , Tnsnames, Listener Host string etc everything connected.

At the time of installation whether all the packages CAT**** were executed at the server, since you have created the sample database then only access will be done.
Registry chekup in windows environment.
In Unix flavour, Export the Profile paths etc.( wonder any chance to create a sample database Here).

check out all the possible rules pertained to the database.

VAST