What kind of setup do I need to use apex_web_service.make_rest_request???

Our DBA has installed APEX in DB19C environment. I am trying to invoke REST Web API (.NetCore) from Oracle PL/SQL.

After back and forth with the network team I have finally made it working after ACL entries in the network using the following

l_http_request := sys.UTL_HTTP.begin_request (l_url,'GET','HTTP/1.1');

But invoking the same REST Web API with the following

l_response := apex_web_service.make_rest_request(p_url => l_url,p_http_method => 'GET');

It does not work. Indeed I am missing some kind of setup for this APEX package.