Problem to access into Comment display "field" and other tab

Hi everyone,

I want to change the render of the postdate fields (to add the hour) in the configuration of the Comment Display but I get an error 403 access forbidden.

The problem is that I'm on an Administrator account with full rights and the error only occurs on the site hosted (I can access on my local).
Access to settings of other sub-module (Node Display, View Display) I may ...
I tried to reinstall the module but nothing changes...

Where do you think it can come?
Thank you in advance,

Sincerely,

Thib