Preview of posts/page… even display any site leads to 404

Valued Support-Team,

we need your help to fix this 404 problem which comes up as soon as we would like to preview a page or post we just entered.

The same 404 screen is displayed when we are clicking on a frontend page and unfortunately this hassle occurs also on all sub domains not only on the main domain.

Looking forward being supported by you.

Kind regards

Prinz