Google translation: "bonjour, Suddenly, during an export request, the export settings window displays all the "Resize" and "Watermark" checkboxes in gray, impossible to check them. does anyone have any idea where it could be coming from? thank you Totoz"
You may have checked a preset in the left side of the Export settings window:

rather than simply selecting it:

That can cause the individual settings fields to grey out.
If this doesn't solve the problem, then in addition to providing the LR version number, please post a screenshot of the entire Export window.