The goal here is to total the Sales Data related to each account for each distributor.  Then see which is the #1 distributor for each account then update the account to reflect that.  My code is throwing no errors, but it isnt updating the field.  Wheres the issue here? I cant find it at all.

Thought it was the SOQL query, but went throug hthat many times and thats definitely pulling the data i want.

Take a look.  Also im pretty new to this so stylistic recommendations are helpful too.

trigger DistributorIDs on Sales_data__c (after insert, after update) {
       Double Amount = 0;
       Double UpdateMap = 0;
       ID PrimaryDistributor;
       Date AfterDate = Date.today().addDays(-45);
       Set<Id>accountIds = new Set<Id>(); //account in trigger.new
       Map<ID, Double> DistributorsList = new Map<ID, Integer>(); //distributors in trigger.new
       for (Sales_data__c Sd: Trigger.new) {
           if(Sd.End_user__c!=null && Sd.Distributor__r!=null){
                accountIds.add(Sd.End_user__c); // adding accounts to set
                DistributorsList.put(Sd.Distributor__c, 0);  // adding distributors to map
           }
       } 
       Map<ID, Double> DistributorsCopy = DistributorsList.clone(); //clone 0'd map

       List<Account> accountToUpdate = new List<Account>(); //list for DML
       List<Account> accList = new List<Account>([SELECT Id,(SELECT Distributor__c,Amount__c,Date__c FROM 
                                                 Sales_data1__r WHERE Date__c >= :AfterDate) // used sub query on Sales Data
                                                 FROM Account WHERE Id IN :accountIds]);
       for(Account acc : accList){ //looping through every account of above list
            for(Sales_Data__c sd : acc.Sales_Data__r){  // looping thorugh every child of the account
                if(sd.Amount__c !=null && sd.Distributor__c!=''){
                    UpdateMap = DistributorsList.get(sd.Distributor__c) + sd.Amount__c; //populate var w updated amt for ea dist
                    DistributorsList.remove(sd.Distributor__c);  //remove old value from map
                    DistributorsList.put(sd.Distributor__c, UpdateMap); //push new one value to map
                 }  
            }
            for (Id key: DistributorsList.keySet()) { //iterate through distributors map
                if(DistributorsList.get(key) > Amount){ //if greater than 0 to start, then greater than max
                    PrimaryDistributor = key;  //set primarydist = key if its greatest so far
                    Amount = DistributorsList.get(key); //set amount equal to value
                }
            }           
            acc.Acct_Primary_Distributor__c = PrimaryDistributor;   // adding largest distributors ID to parent account
            accountToUpdate.add(acc);
            DistributorsList.clear(); //returning map values to 0 before next iteration
            DistributorsList.putAll(DistributorsCopy);
          } 
      if(accountToUpdate.size() > 0){
        update accountToUpdate;
      }
}