Salesforce Deployment: Method does not exist or incorrect signature"

Question

I have a Apex Class which is having a issue when I am deploying via Package. When I save the class in Developer Console it is not a issue, but due to this my CICD is not working and I need to resolve this.

I am calling a method like this:

record.Date_time_Registration_Response_Provided__c = IDRCaseActionsHelper.populateAfcaRegistrationResponseDate(
      oldRecord,
      record
    );

and this method is implemented as follows:

  /**
   * @description Populate Date/time Registration Response Provided when AFCA Registration Response Provided is checked
   * @param oldRecord old Record of pre-update cases supplied from the trigger as well
   * @param newRecord new Record of cases from the trigger
   * @return DateTime
   */
  public static DateTime populateAfcaRegistrationResponseDate(
    Case oldRecord,
    Case newRecord
  ) {
    if (
      oldRecord.IDR_AFCA_Registration_Response_Provided__c ==
      newRecord.IDR_AFCA_Registration_Response_Provided__c
    ) {
      return newRecord.Date_time_Registration_Response_Provided__c;
    }

    if (!newRecord.IDR_AFCA_Registration_Response_Provided__c) {
      return newRecord.Date_time_Registration_Response_Provided__c;
    }
    return DateTime.now();
  }

I am getting following error

Method does not exist or incorrect signature: void populateAfcaRegistrationResponseDate(Case, Case) from the type CLASSNAME

now I don't get why it is searching or void when I need it as DateTime type only....