First, I've never actually used Frontier::Client. Second, if I was inclined to use it, I would probably go with something like this:

#!/usr/bin/perl -l

use strict;
use warnings;
use LWP::UserAgent;
use Frontier::Client;
use Data::Dumper::Concise;

my $ua  = LWP::UserAgent->new(
    ssl_opts => { verify_hostname => 0 },
    protocols_allowed => ['https'],
);

my $req = HTTP::Request->new( 
    GET => 'https://pause.perl.org',
);

my $res = $ua->request($req);
print $res->code;

my $server = Frontier::Client->new(
    url      => 'https://pause.perl.org',
    encoding => 'ISO-8859-1',
    debug    => 1,
);

my $date_time = $server->call('date_time');
print Dumper( $date_time );
[download]

I was was just trying to make it work, so feel free to add to or subtract from ssl_opts. Good luck:-).