Fatal error: Uncaught Error: Call to undefined function is_main_site() in /usr/home/taiyang3690/domains/chinafastener.site/public_html/wp-includes/update.php:1145
Stack trace:
#0 {main}
  thrown in /usr/home/taiyang3690/domains/chinafastener.site/public_html/wp-includes/update.php on line 1145