plugin: silver searcher doesn't find installed executable

I enabled the SilverSearcher Plugin in QT Creator (described here: https://doc.qt.io/qtcreator/creator-editor-finding.html#enabling-silver-searcher) and installed the SilverSearcher executable with homebrew. Then i restarted Qt Creator and tried to use the plugin. But when i select Silver Searcher as the Search engine in Advanced Find, Creator shows "Silver Searcher is not available on the system".

I can execute "ag --version" without problems in terminal. ag is installed in /usr/local/bin/ag.

QProcess silverSearcherProcess; silverSearcherProcess.start("ag", {"--version"});
if (silverSearcherProcess.waitForFinished()){
    if (silverSearcherProcess.readAll().contains("ag version"))
        qDebug() << "ag is Installed!";
    else 
        qDebug() << "ag NOT found!";
}

if i build & run this code snippet, it also shows that: "ag is Installed!"

I cannot find any hints to this problem online. I have 2 Macs which are both affected.

Any help is greatly appreciated. Thanks.