$root appears to be blank

No, it returns what it should

use XML::Bare;
use Data::Dumper;

my $page = '<?xml version="1.0" encoding="ISO-8859-1" ?> 
<PayoneerResponse>
<Echo>
<Status>000</Status> 
<Description>Echo Ok - All systems are up.</Description> 
</Echo>
</PayoneerResponse>';
  
my $ob = new XML::Bare( text => $page );
my $root = $ob->parse();

local $Data::Dumper::Indent = 1;
print(Dumper($root));
[download]

$VAR1 = {
  '_z' => 0,
  '_i' => -26338708,
  'PayoneerResponse' => {
    '_z' => 178,
    '_i' => 47,
    'value' => '
',
    '_pos' => 1,
    'Echo' => {
      '_z' => 158,
      '_i' => 66,
      'Status' => {
        '_z' => 91,
        '_i' => 73,
        'value' => '000',
        '_pos' => 3
      },
      'value' => '
',
      '_pos' => 2,
      'Description' => {
        '_z' => 149,
        '_i' => 95,
        'value' => 'Echo Ok - All systems are up.',
        '_pos' => 4
      }
    }
  },
  'value' => '
',
  '_pos' => 0
};
[download]

They never put an ending '</xml>'

Nor should they. The root element is named PayoneerResponse, not xml.

What would You use to parse the response from them?

Of the parsers I've tried, XML::LibXML is by far the fastest, it has a good interface, and actually handles namespaces correctly. It is my XML parser of choice.