Hi guys, I've used Formidable in many projects but never incurred in this error.
Whenever I try to activate the conversational forms addon, I receive this warning: 

Fatal error: Uncaught TypeError: Cannot access offset of type string on string in /home/mhd-01/www.ddomiapiovedisacco.com/htdocs/wp-content/plugins/formidable-chat/classes/models/FrmChatStyleTemplateApi.php:85 Stack trace: #0 /home/mhd-01/www.ddomiapiovedisacco.com/htdocs/wp-content/plugins/formidable-chat/classes/models/FrmChatStyleTemplateApi.php(73): FrmChatStyleTemplateApi->get_download_url_for_style() #1 /home/mhd-01/www.ddomiapiovedisacco.com/htdocs/wp-content/plugins/formidable-chat/classes/models/FrmChatStyleTemplateApi.php(50): FrmChatStyleTemplateApi->get_chat_form_style_url() #2 /home/mhd-01/www.ddomiapiovedisacco.com/htdocs/wp-content/plugins/formidable-chat/formidable-chat.php(114): FrmChatStyleTemplateApi->install_style() #3 /home/mhd-01/www.ddomiapiovedisacco.com/htdocs/wp-includes/class-wp-hook.php(310): frm_update_stylesheet_on_activation() #4 /home/mhd-01/www.ddomiapiovedisacco.com/htdocs/wp-includes/class-wp-hook.php(334): WP_Hook->apply_filters() #5 /home/mhd-01/www.ddomiapiovedisacco.com/htdocs/wp-includes/plugin.php(517): WP_Hook->do_action() #6 /home/mhd-01/www.ddomiapiovedisacco.com/htdocs/wp-admin/plugins.php(194): do_action() #7 {main} thrown in /home/mhd-01/www.ddomiapiovedisacco.com/htdocs/wp-content/plugins/formidable-chat/classes/models/FrmChatStyleTemplateApi.php on line 85

I cannot understand what to do to solve it.

Do you have any clues?