Fatal error: No valid public key for reCaptcha found.

Information:

error message: No valid public key for reCaptcha found.
error code: 0
file: /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/util/ReCaptchaUtil.class.php (66)
php version: 5.6.17-0+deb8u1
wcf version: 1.1.9 (Tempest)
date: Thu, 18 Apr 2024 15:50:39 +0000
request: /forum/index.php?form=Mail&userID=2010&s=2d9782f89a6b9af0ed4aa61dcfa384ffe4f2e72d
referer:

Stacktrace:

#0 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/system/event/listener/CaptchaFormReCaptchaListener.class.php(78): ReCaptchaUtil::getPublicKey()
#1 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/system/event/listener/CaptchaFormReCaptchaListener.class.php(40): CaptchaFormReCaptchaListener->assignVariables(Object(MailForm))
#2 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/system/event/EventHandler.class.php(131): CaptchaFormReCaptchaListener->execute(Object(MailForm), 'MailForm', 'assignVariables')
#3 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/system/event/EventHandler.class.php(156): EventHandler::executeInheritedActions(Object(MailForm), 'assignVariables', 'MailForm', 'assignVariables...')
#4 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/page/AbstractPage.class.php(73): EventHandler::fireAction(Object(MailForm), 'assignVariables')
#5 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/form/AbstractForm.class.php(100): AbstractPage->assignVariables()
#6 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/form/CaptchaForm.class.php(117): AbstractForm->assignVariables()
#7 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/form/MailForm.class.php(132): CaptchaForm->assignVariables()
#8 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/page/AbstractPage.class.php(93): MailForm->assignVariables()
#9 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/form/MailForm.class.php(154): AbstractPage->show()
#10 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/page/AbstractPage.class.php(46): MailForm->show()
#11 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/util/RequestHandler.class.php(64): AbstractPage->__construct()
#12 /srv/vhosts/newrockwood.de/htdocs/forum/wcf/lib/util/RequestHandler.class.php(95): RequestHandler->__construct('Mail', Array, 'form')
#13 /srv/vhosts/newrockwood.de/htdocs/forum/index.php(14): RequestHandler::handle(Array)
#14 {main}