With this code, when I execute the query in the inspector I get the result, however when I call my class in my component I do not retrieve Data and I get this error in the console:

      message : "expecting a right parentheses"

and tells me that the error that exists in the last line of code:

     cumul = database.query(Query);

some help please .

 @AuraEnabled(cacheable=true)
    public static List <AggregateResult> getMonthly(){
    User u = [SELECT id, Volume__c FROM  User WHERE id=: UserInfo.getUserId()];
    List<AggregateResult> cumul = new list<AggregateResult>();
    List<Account> acc = [SELECT Id,RecordType.DeveloperName FROM Account WHERE ownerid =: UserInfo.getUserId()];
    List<String> accString = new List<String>();
        for( Account c: acc)
            {
            accString.add(c.Id);
            }
    String year = String.valueOf(System.Today().year());
    String  productFamily = 'light';
    String Filters ='';
    Filters = Filters + 'Year__c = \'' + year +'\' ';
    Filters = Filters + 'AND Sales__r.Account__r.Station_Account__c IN '+ accString +' ';    
    Filters = Filters + 'AND Product_Family__c = \''+ productFamily +'\' ';
    String Query = 'SELECT Sales__r.Account__r.Name ,CALENDAR_MONTH(Date_technicalfield__c) Month, ';    
        if (u.Volume__c == 'Liter') {
            Query = Query + 'SUM(Quantity_in_L__c) Quantity ';
        } else {
            Query = Query + 'COUNT(id) Quantity ';
        }
        Query = Query + 'FROM SalesK__c WHERE ' + Filters + 'GROUP BY CORE__r.Account__r.Name ,Date_technicalfield__c ORDER BY Date_technicalfield__c ASC';
    cumul = database.query(Query);
    return cumul;
    }

With this code, when I execute the query in the inspector I get the result, however when I call my class in my component I do not retrieve Data and I get this error in the console:

      message : "expecting a right parentheses"

and tells me that the error that exists in the last line of code:

     cumul = database.query(Query);

some help please .

 @AuraEnabled(cacheable=true)
    public static List <AggregateResult> getMonthly(){
    User u = [SELECT id, Volume__c FROM  User WHERE id=: UserInfo.getUserId()];
    List<AggregateResult> cumul = new list<AggregateResult>();
    List<Account> acc = [SELECT Id,RecordType.DeveloperName FROM Account WHERE ownerid =: UserInfo.getUserId()];
    List<String> accString = new List<String>();
        for( Account c: acc)
            {
            accString.add(c.Id);
            }
    String year = String.valueOf(System.Today().year());
    String  productFamily = 'light';
    String Filters ='';
    Filters = Filters + 'Year__c = \'' + year +'\' ';
    Filters = Filters + 'AND Sales__r.Account__r.Station_Account__c IN '+ accString +' ';    
    Filters = Filters + 'AND Product_Family__c = \''+ productFamily +'\' ';
    String Query = 'SELECT Sales__r.Account__r.Name ,CALENDAR_MONTH(Date_technicalfield__c) Month, ';    
        if (u.Volume__c == 'Liter') {
            Query = Query + 'SUM(Quantity_in_L__c) Quantity ';
        } else {
            Query = Query + 'COUNT(id) Quantity ';
        }
        Query = Query + 'FROM SalesK__c WHERE ' + Filters + 'GROUP BY Sales__r.Account__r.Name ,Date_technicalfield__c ORDER BY Date_technicalfield__c ASC';
    cumul = database.query(Query);
    return cumul;
    }