Please let me what this means and how to fix it. Host insists it is not at their end.

Full error message
Installing: Error: Authentication type with handle concrete already exists!. Trace: #0 /home/acthome/public_html/celebrationgeneration.com.au/concrete/src/Package/StartingPointPackage.php(296): Concrete\Core\Authentication\AuthenticationType::add('concrete', 'Standard') #1 [internal function]: Concrete\Core\Package\StartingPointPackage->add_users() #2 /home/acthome/public_html/celebrationgeneration.com.au/concrete/controllers/install.php(264): call_user_func(Array) #3 [internal function]: Concrete\Controller\Install->run_routine('elemental_blank', 'add_users') #4 /home/acthome/public_html/celebrationgeneration.com.au/concrete/src/Controller/AbstractController.php(156): call_user_func_array(Array, Array) #5 /home/acthome/public_html/celebrationgeneration.com.au/concrete/src/Routing/ControllerRouteCallback.php(25): Concrete\Core\Controller\AbstractController->runAction('run_routine', Array) #6 /home/acthome/public_html/celebrationgeneration.com.au/concrete/src/Routing/Router.php(59): Concrete\Core\Routing\ControllerRouteCallback->execute(Object(Concrete\Core\Http\Request), Object(Concrete\Core\Routing\Route), Array) #7 /home/acthome/public_html/celebrationgeneration.com.au/concrete/src/Support/Facade/Facade.php(119): Concrete\Core\Routing\Router->execute(Object(Concrete\Core\Routing\Route), Array) #8 /home/acthome/public_html/celebrationgeneration.com.au/concrete/src/Application/Application.php(366): Concrete\Core\Support\Facade\Facade::__callStatic('execute', Array) #9 /home/acthome/public_html/celebrationgeneration.com.au/concrete/src/Application/Application.php(366): Concrete\Core\Support\Facade\Route::execute(Object(Concrete\Core\Routing\Route), Array) #10 /home/acthome/public_html/celebrationgeneration.com.au/concrete/bootstrap/start.php(217): Concrete\Core\Application\Application->dispatch(Object(Concrete\Core\Http\Request)) #11 /home/acthome/public_html/celebrationgeneration.com.au/concrete/dispatcher.php(36): require('/home/acthome/p...') #12 /home/acthome/public_html/celebrationgeneration.com.au/index.php(2): require('/home/acthome/p...') #13 {main}