[Typo3] Flexform tabs don't show

[Eduard Renger]

Hi list,

I have a problem with several of my extensions that use flexforms. The
only thing I see in BE are the tabs. e.g. in tt_news I just see:
 Plugin Options:
 General Settings Template Category Settings Other Settings


The actual contents of the tabs don't show anymore. So I can't change any
settings for content items using those extensions. This used to work
before.

This is the case for the following extensions I have installed:
Better Login-box
CHC Forum
Extended calendar
News
All the above extensions have more than one tab

The following extensions using flexforms do work. None of them has more
than one tab:
User Listing (no tabs, just fields)
CWT Community (only one tab)
Who is online (only one tab)
CMW Linklist (only one tab)

Does anyone know how to solve this?

I Use Typo 3.7

greetings,
Eduard Renger