Error!: SQLSTATE[01002] Adaptive Server connection failed (severity 9)

Recoverable error: Argument 1 passed to register\user::__construct() must be an instance of PDO, null given, called in /var/www/massenversand_neu/massenversand-anmeldeprozess/goyyamobile_register.php on line 12 and defined in massenversand-anmeldeprozess/mod_registeraccount/classes/user.php on line 300
#0 massenversand-anmeldeprozess/mod_registeraccount/classes/user.php(300): __error(4096, 'Argument 1 pass...', '/var/www/massen...', 300, Array)
#1 massenversand-anmeldeprozess/goyyamobile_register.php(12): register\user->__construct(NULL)
#2 templates/maintemplates/anmeldeprozess.php(4): include('/var/www/massen...')
#3 system/modules/core/library/Contao/InsertTags.php(1113): include('/var/www/massen...')
#4 system/modules/core/library/Contao/Controller.php(692): Contao\InsertTags->replace('...', false)
#5 system/modules/core/classes/FrontendTemplate.php(100): Contao\Controller::replaceInsertTags('...', false)
#6 system/modules/core/pages/PageRegular.php(190): Contao\FrontendTemplate->output(true)
#7 system/modules/core/controllers/FrontendIndex.php(285): Contao\PageRegular->generate(Object(Contao\PageModel), true)
#8 index.php(20): Contao\FrontendIndex->run()
#9 {main}

Fatal error: Call to a member function prepare() on a non-object in /var/www/massenversand_neu/massenversand-anmeldeprozess/mod_registeraccount/classes/user.php on line 737