Fourth footer sidebar is not showing up in customizer anymore

Hello,

the installation of the MercantilePro theme went well and was very easy. I switched the footer options to 4 segments, and at first all four footer sidebar areas were shown, but as of late, I cannot see the fourth footer sidebar anymore. And I have no clue where to investigate to bring it back.

I added all relevant screenshots which I think are correct.
Any help or hint would be nice.

Description from top to down:
1) View of the available footer sidebars.
2) View of the footer section of the landing page.
3) Footer options in the customizer.
4) Available widgets in the widgets section.

Regards
Steffen

• This topic was modified 4 years ago by Steffen Hölscher. Reason: added descriptions for the images