Error When Creating New Site On WordPress MU Subdomain

Hello,
I need help about this. I get error when creating new subsite through Network Dashboard, it said “Are you sure you want to do this?” and “WordPress Failure Notice” on tab also the button only “Please try again”. Wildcard has been added on DNS and Cloudflare CDN. .htaccess and wp-config with “define(‘SUBDOMAIN_INSTALL’, true);” also has been set up. What am I missing here? could someone help me with this? thank you.
[img]https://s19.postimg.org/jm2yr9y4f/image.png[/img]

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