I’m follow this tutorial > https://www.digitalocean.com/community/tutorials/php-fpm-nginx
Your theme is apparently trying to save files, but it isn’t working because the file permissions are probably not right. In this case, WordPress switches to FTP, which in turn doesn’t work because the libraries for it are missing. The PHP message is therefore just a follow-up error.
Take a close look to see whether the directory and file permissions in the file system match those stored in your nginx configuration. See also: https://developer.projectdmc.org/advanced-administration/server/file-permissions/
I’m manage to solve by change user/goup in php-fpm pool name.
Glad you were able to solve it. You can also mark the topic as solved.