I get the following error using remind of a survey

$cant_mails2 = $client->sSendEmail(LS_USER, LS_PASS, $iVid, 'remind');

Error:
Fatal error: Uncaught SoapFault exception: [SOAP-ENV:Server] Call to a member function RecordCount() on a non-object in
Stack trace:
#0 : SoapClient->__call('sSendEmail', Array)
#1 : SoapClient->sSendEmail('admin', 'password', '460', 'remind')
#2 : integrar('26') #3 {main} thrown in