The website encountered an unexpected error on Drupal9.1

I am using reCAPTCHA on user registration, after user click "create new account", the site broken. I printed the error on the screen which is showing below:

The website encountered an unexpected error. Please try again later.
Error: Class 'ReCaptcha\ReCaptcha' not found in recaptcha_captcha_validation() (line 162 of modules/recaptcha/recaptcha.module).
recaptcha_captcha_validation('1', 'Google no captcha', Array, Object) (Line: 501)
captcha_validate(Array, Object, Array)
call_user_func_array('captcha_validate', Array) (Line: 280)
Drupal\Core\Form\FormValidator->doValidateForm(Array, Object) (Line: 236)
Drupal\Core\Form\FormValidator->doValidateForm(Array, Object, 'user_register_form') (Line: 118)
Drupal\Core\Form\FormValidator->validateForm('user_register_form', Array, Object) (Line: 589)
Drupal\Core\Form\FormBuilder->processForm('user_register_form', Array, Object) (Line: 321)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)
Drupal\Core\Controller\FormController->getContentResult(Object, Object) (Line: 39)
Drupal\layout_builder\Controller\LayoutBuilderHtmlEntityFormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 573)
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}() (Line: 158)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 80)
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: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 706)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)