Cannot add trainings because no moxtra account

The full error message is that this error appears in the dblog every second：

Deprecated function: Creation of dynamic property Drupal\opigno_moxtra\MoxtraService::$httpClient is deprecated in Drupal\opigno_moxtra\MoxtraService->__construct() (line 74 of /home/wwwroot/kstudy/web/modules/contrib/opigno_moxtra/src/MoxtraService.php)
#0 /home/wwwroot/kstudy/web/core/includes/bootstrap.inc(164): _drupal_error_handler_real()
#1 /home/wwwroot/kstudy/web/modules/contrib/opigno_moxtra/src/MoxtraService.php(74): _drupal_error_handler()
#2 /home/wwwroot/kstudy/web/core/lib/Drupal/Component/DependencyInjection/Container.php(259): Drupal\opigno_moxtra\MoxtraService->__construct()
#3 /home/wwwroot/kstudy/web/core/lib/Drupal/Component/DependencyInjection/Container.php(177): Drupal\Component\DependencyInjection\Container->createService()
#4 /home/wwwroot/kstudy/web/core/lib/Drupal/Component/DependencyInjection/Container.php(440): Drupal\Component\DependencyInjection\Container->get()
#5 /home/wwwroot/kstudy/web/core/lib/Drupal/Component/DependencyInjection/Container.php(237): Drupal\Component\DependencyInjection\Container->resolveServicesAndParameters()
#6 /home/wwwroot/kstudy/web/core/lib/Drupal/Component/DependencyInjection/Container.php(177): Drupal\Component\DependencyInjection\Container->createService()
#7 /home/wwwroot/kstudy/web/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php(105): Drupal\Component\DependencyInjection\Container->get()
#8 /home/wwwroot/kstudy/vendor/symfony/http-kernel/HttpKernel.php(157): Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch()
#9 /home/wwwroot/kstudy/vendor/symfony/http-kernel/HttpKernel.php(76): Symfony\Component\HttpKernel\HttpKernel->handleRaw()
#10 /home/wwwroot/kstudy/web/core/lib/Drupal/Core/StackMiddleware/Session.php(58): Symfony\Component\HttpKernel\HttpKernel->handle()
#11 /home/wwwroot/kstudy/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle()
#12 /home/wwwroot/kstudy/web/core/lib/Drupal/Core/StackMiddleware/ContentLength.php(28): Drupal\Core\StackMiddleware\KernelPreHandle->handle()
#13 /home/wwwroot/kstudy/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\Core\StackMiddleware\ContentLength->handle()
#14 /home/wwwroot/kstudy/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass()
#15 /home/wwwroot/kstudy/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\page_cache\StackMiddleware\PageCache->handle()
#16 /home/wwwroot/kstudy/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()
#17 /home/wwwroot/kstudy/web/core/lib/Drupal/Core/StackMiddleware/AjaxPageState.php(36): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()
#18 /home/wwwroot/kstudy/web/core/lib/Drupal/Core/StackMiddleware/StackedHttpKernel.php(51): Drupal\Core\StackMiddleware\AjaxPageState->handle()
#19 /home/wwwroot/kstudy/web/core/lib/Drupal/Core/DrupalKernel.php(704): Drupal\Core\StackMiddleware\StackedHttpKernel->handle()
#20 /home/wwwroot/kstudy/web/index.php(19): Drupal\Core\DrupalKernel->handle()
#21 {main}