Unable to access plugin

Thank you for sharing that information !

This confirms what I already suspected, it must be a plugin conflict.
Still I do think a minor code fix to the iTSec plugin can potentially prevent this particular conflict.

I updated this topic with the code fix I have in mind. Looking for confirmation that it fixes the issue from the field ??

To prevent any confusion, I’m not iThemes.

Just some extra background info. It turns out that the bsf (Brainstorm Force) license manager bundled with UAEL (Ultimate Addons for Elementor) is causing this issue. On every admin request it is (programmatically) adding an entry to the $_POST superglobal, which is not what it is for. The $_POST superglobal should only hold data when doing a POST request (like submitting a form).

Since the iTSec plugin Settings page always checks whether $_POST is not empty, a simple GET request to the page triggers the Settings page POST action. Consequently it’s nonce check fails.

Anyway, are you using a purchased license of the UAEL plugin ?
Or was it some dodgy unofficial copy ?