I am writing for an update. I was able to understand the problem.
It does not depend on the server configuration or other settings but simply on the name of the folder that contains the website in localhost. For one of my organizations I prefix the folder name with a numeric code (example 001_Name_folder). This puts the plugin in error (absolutely strange, also because you don't have problems with other CB plugins or other Joomla components, modules and plugins). By deleting the number from the folder name (example Name_folder) everything works perfectly again. It took 8 months to understand this and maybe it can be useful for other users or plugin developers to know to prevent the error. Thanks for the support.