i run a WordPress web site and i try to use a ssl plugin the plugin ask me to create a hidden folder .well-known/acme-challeng and when i try to test it its blocked please advice how to allow the access
This folder is used by Let's encrypt and managed by the system, so you can not create it in the website. Instead of using an SSL plugin for Wordpress, you can enable SSL and let#s encrypt for that website in ISPConfig.