Hello.
I am having the same problem.
I removed it once and reinstalled it using the method above.
But the problem was not solved.
Multisite WP5.9.2
W3 Total Cache 2.2.1
こちら2.4.5でも下記行でエラー同じエラーだったのでご報告させていただきます。
Warning: count(): Parameter must be an array or an object that implements Countable in /home/kusanagi/kusanagi_html/DocumentRoot/wp-content/plugins/custom-field-template/custom-field-template.php on line 1977
