Hi Stefano,
is there a bug in wp-content\plugins\newsletter\emails\tnp-composer\blocks\header-01-header.block.php
<?php echo isset($block_options['header_logo']) ? $block_options['header_logo']['url'] : 'http://placehold.it/180x50?text=' . isset($block_options['header_title']) ? $block_options['header_title'] : "" ?>
I think it must be
<?php echo isset($block_options['header_logo']) ? $block_options['header_logo']['url'] : 'http://placehold.it/180x50?text=' . isset($block_options['header_title']) ?>
Greetings,
Farant