Widgets settings seem to be not responsive

Dear all,
I am facing these issues.

I have a blog page in my website; blog posts are correctly appearing.

I am trying to set up some widgets, but I have only been able to have the Search widget displayed in the sidebar. I have put it alternatively in “Sidebar blog” and in “Displayed everywhere”

I have tried to set up several other widgets (facebook page code and LinkedIn follow my page code) aiming to have them displayed in the “Sidebar blog” or in the “Displayed everywhere”, but they are not displayed.

After I deleted the “search” widget from “Sidebar blog”, I have “Pages”, “Categories”, “Archives”. These must be set by default in some way, because no widget appears now in any of the sidebars.

So I have created a new different sidebar (and put there an e-mail newsletter subscription widget).
I tried to set the blog post to show the new sidebar. When I click save, it wont accept my new sidebar; it will save it with “default sidebars”
The same thing happens with the “blog” page. I tried to have my newly set sidebar to be shown, but when I click save I have no success: only “default sidebars”.

I hope you can help me out.
Many thanks.