Call to undefined function wp_tempnam

Hello, what’s the problem with the following?

Fatal error: Uncaught Error: Call to undefined function wp_tempnam() in /home/”“/public_html/wp-admin/includes/class-wp-filesystem-ftpext.php:163 Stack trace: #0 /home/”“/public_html/wp-content/plugins/upload-to-ftp/class.ry-ftp.php(203): WP_Filesystem_FTPext->put_contents(‘/2019/01/Portal…’, ‘x89PNGrnx1Anx00x00x00rIHD…’) #1 /home/”“/public_html/wp-content/plugins/upload-to-ftp/class.ry-ftp.php(176): RY_FTP::do_upload_file(‘/2019/01/Portal…’, ‘/home/”“/p…’) #2 /home/”“/public_html/wp-content/plugins/upload-to-ftp/class.ry-ftp.php(80): RY_FTP::do_ftp_upload() #3 /home/”“/public_html/wp-includes/class-wp-hook.php(286): RY_FTP::set_upload_file(Array, 39122) #4 /home/”“/public_html/wp-includes/plugin.php(208): WP_Hook->apply_filters(Array, Array) #5 /home/”“/public_html/wp-includes/post.php(5581): apply_filters(‘wp_update_attac…’, Array, 39122) #6 /home/”“/public_html/wp-content/plugins/woocommerce/includes/class-wc-regenerate-images.php(371): wp_update_attachmen in /home/”“/public_html/wp-admin/includes/class-wp-filesystem-ftpext.php on line ???