following error message appears when the plugin is activated:

<b>Fatal error</b>: Uncaught Error: Call to undefined method TGM_Plugin_Activation::is_tgmpa_complete() in /www/htdocs/w013bc10/onelife.eco/wp/wp-content/themes/jevelin/inc/core/dashboard-header.php:66 Stack trace: #0 /www/htdocs/w013bc10/onelife.eco/wp/wp-content/themes/jevelin/inc/core/dashboard-header.php(202): sh_tgmpa_header() #1 /www/htdocs/w013bc10/onelife.eco/wp/wp-includes/class-wp-hook.php(287): sample_admin_notice__success(”) #2 /www/htdocs/w013bc10/onelife.eco/wp/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array) #3 /www/htdocs/w013bc10/onelife.eco/wp/wp-includes/plugin.php(478): WP_Hook->do_action(Array) #4 /www/htdocs/w013bc10/onelife.eco/wp/wp-admin/admin-header.php(284): do_action(‘admin_notices’) #5 /www/htdocs/w013bc10/onelife.eco/wp/wp-admin/admin.php(239): require_once(‘/www/htdocs/w01…’) #6 /www/htdocs/w013bc10/onelife.eco/wp/wp-admin/themes.php(10): require_once(‘/www/htdocs/w01…’) #7 {main} thrown in <b>/www/htdocs/w013bc10/onelife.eco/wp/wp-content/themes/jevelin/inc/core/dashboard-header.php</b> on line <b>66</b>