Template file is expected to be in public directory

[sboetzel]

I have installed tt-board via composer at TYPO3 12.4., added the static template files, set up the pagetree with the board plugins for list and single. I've added the needed group-Configuration to typoscript.

In the frontend appears an error:
InvalidFileException: "EXT:tt_board/Resources/Private/Templates/board_template1.tmpl" is expected to be in public directory, but is not, in file /html/typo3-composer/vendor/typo3/cms-core/Classes/Utility/PathUtility.php:107

The invalid template-file is in the folder
/html/typo3-composer/vendor/jambagecom/tt-board/Resources/Private/Templates/board_template1.tmpl

I run chmod -R g+w on all files and folders in my composer-directory,
but the error still appears.

Can someone help me?

I use
TYPO3 12.4.22
php 8.2.25
EXT:bootstrap_package 15.0
EXT:tt_board 1.15.1