WP 5.2.2 detects erros and restrict admin access

WP 5.2.2 detects erros and restrict admin access. I had to delete your plugin via ftp to gain access to my admin section. I go an automatic email error message sent by WP from my site. Below. Kindly look in to it.

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Error Details
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An error of type E_ERROR was caused in line 326 of the file /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/404page/inc/class-404page-admin.php. Error message: Uncaught Error: Call to undefined method PP_404Page::get_asset_file() in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/404page/inc/class-404page-admin.php:326
Stack trace:
#0 /opt/bitnami/apps/wordpress/htdocs/wp-includes/class-wp-hook.php(286): PP_404Page_Admin->admin_js(‘appearance_page…’)
#1 /opt/bitnami/apps/wordpress/htdocs/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array)
#2 /opt/bitnami/apps/wordpress/htdocs/wp-includes/plugin.php(465): WP_Hook->do_action(Array)
#3 /opt/bitnami/apps/wordpress/htdocs/wp-admin/admin-header.php(104): do_action(‘admin_enqueue_s…’, ‘appearance_page…’)
#4 /opt/bitnami/apps/wordpress/htdocs/wp-admin/admin.php(233): require_once(‘/opt/bitnami/ap…’)
#5 /opt/bitnami/apps/wordpress/htdocs/wp-admin/themes.php(10): require_once(‘/opt/bitnami/ap…’)
#6 {main}
thrown
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do let me know what this is. in the meantime, i am forced to delete your plugin and use an alternative, though i liked yours very much. I cannot test by deactivating other plugins as it is a live site.

Thanks