How to update salesforce custom object (Customer__c) OptIn field value from Marketing cloud (Customer DE) OptIn attribute value using AMP script

I have a scenario, 1 DE (Customer DE with SubscriberKey, OptIn, Status, OptInDate attributes) with some records. I want to update the salesforce Customer__c object records OptIn (Yes/No) if SubscriberKey is matching from MC using AMPScript.

I have tried UpdateSingleSalesforceObject method but results are getting empty. below is the code which i tried.

%%[var @resultset @result = UpdateSingleSalesforceObject('Customer__c', @SubscriberKey,'Mobile_Number__c', @MobileNumber,'Promo_Pref__c',@SMSOptIn)]%%

Also considering this is for multiple records update.