Problem when configurating WP to Buffer

Hello everyone,

I have a problem when I try to configure WP to Buffer plugin in my wordpress website.

When I want to connect my Buffet account with the pluggin I have an error message :

Fatal error: Uncaught Error: Call to a member function get_error_message() on null in /srv/disk1/2704562/www/my-smart-personal-finances.co.nf/wp-content/plugins/wp-to-buffer/vendor/includes/admin/admin.php:116 Stack trace: #0 /srv/disk1/2704562/www/my-smart-personal-finances.co.nf/wp-includes/class-wp-hook.php(286): WP_To_Social_Pro_Admin->oauth(”) #1 /srv/disk1/2704562/www/my-smart-personal-finances.co.nf/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array) #2 /srv/disk1/2704562/www/my-smart-personal-finances.co.nf/wp-includes/plugin.php(453): WP_Hook->do_action(Array) #3 /srv/disk1/2704562/www/my-smart-personal-finances.co.nf/wp-settings.php(450): do_action(‘init’) #4 /srv/disk1/2704562/www/my-smart-personal-finances.co.nf/wp-config.php(91): require_once(‘/srv/disk1/2704…’) #5 /srv/disk1/2704562/www/my-smart-personal-finances.co.nf/wp-load.php(37): require_once(‘/srv/disk1/2704…’) #6 /srv/disk1/2704562/www/my-smart-personal-finances.co.nf/wp-admin/admin.php(31): require_once(‘/srv/disk1/2704…’) in /srv/disk1/2704562/www/my-smart-personal-finances.co.nf/wp-content/plugins/wp-to-buffer/vendor/includes/admin/admin.php on line 116

WordPress Version : 4.9.5
WP to Buffer Version : 3.3.5
Steps followed : WP to Buffer – Settings > Authorize Plugin > Allow access then the error message appears.

Thanks in advance for your help.