“internal server” error while saving settings

Hello everyone,
I’m trying since this morning to make iTheme security work.

I’ve already installed and used this plugin on other websites (also on some on the same hosting space where I’m trying to use it now!!)

Each time I enter the plugin setting and try to save whatever configuration, it appears this phrase:

A “internal server” error prevented the request from completing as expected. The server returned a 500 status code, indicating that the server was unable to complete the request due to a fatal PHP error or a server problem. This could be due to a plugin/theme conflict, a server configuration issue, a temporary hosting issue, or invalid custom PHP modifications. Please check your server’s error logs for details about the source of the error and contact your hosting company for assistance if required.

Everything else on the website is ok (I’m ready to promote it!). I cannot figure out what is happening… also: i had a look on the log error file provided from my hosting… but no calls appears on the time that i tried to save…

Thank you for your help!

PS .htaccess already re-generated, wp-config memory-limit increased to 128MB

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