Problemas ao instalar um Plugin no WordPress

Ola pessoal,

Instalei um plugin no mei site do wordPress e esta aparecendo varias mensagens de erro e o plugin e o site nao estao funcionando.

Essas são as mensagens que aparecem:

Notice: add_shortcode was called incorrectly. Invalid shortcode name: Empty name given. Please see Debugging in WordPress for more information. (This message was added in version 4.4.0.) in /home/cotacota/public_html/wp-includes/functions.php on line 4986

Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/cotacota/public_html/wp-includes/functions.php:4986) in /home/cotacota/public_html/wp-content/plugins/woo-price-history/aa-framework/ajax-list-table.php on line 66Warning: Cannot modify header information - headers already sent by (output started at /home/cotacota/public_html/wp-includes/functions.php:4986) in /home/cotacota/public_html/wp-includes/functions.php on line 6029Warning: Cannot modify header information - headers already sent by (output started at /home/cotacota/public_html/wp-includes/functions.php:4986) in /home/cotacota/public_html/wp-admin/includes/misc.php on line 1252Warning: Cannot modify header information - headers already sent by (output started at /home/cotacota/public_html/wp-includes/functions.php:4986) in /home/cotacota/public_html/wp-admin/admin-header.php on line 9

Alguem sabe por onde devo começar para corrigir esses erros?

Obrigado