Login issue for review

This module download and enable then logout drupal site login not working properly

Drupal\Core\Database\DriverNotSpecifiedException: Driver not specified for this database connection: external_db_login_connection in Drupal\Core\Database\Database::openConnection() (line 365 of core/lib/Drupal/Core/Database/Database.php).
Drupal\Core\Database\Database::getConnection() (Line: 22)
Drupal\external_db_login\ExternalDBLoginService->testConnection() (Line: 32)
external_db_login_form_alter(Array, Object, 'user_login_form') (Line: 501)
Drupal\Core\Extension\ModuleHandler->alter('form', Array, Object, 'user_login_form') (Line: 819)
Drupal\Core\Form\FormBuilder->prepareForm('user_login_form', Array, Object) (Line: 272)
Drupal\Core\Form\FormBuilder->buildForm('user_login_form', Object) (Line: 74)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 574)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
call_user_func_array(Object, Array) (Line: 144)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 64)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 50)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 656)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)