John, 

That would be amazing if you can figure this out.

---Trigger--
trigger AccountTeamADD on TSG__c (before update,before insert) {

//list to hold new account team members
     List<AccountTeamMember> acctMembers = new List<AccountTeamMember>();
    
     //list to hold new account sharing rules
     List<AccountShare> acctSharingRules = new List<AccountShare>();


//Hold SalesRep
Set <String> ss = New Set<String>();
//Hold Customer ID
Set <String> aa = New Set<String>();
// Hold User Info
List<User> TheUser=new LIST<User>();
//Hold Account Info
List<Account> TheAcct=new LIST<Account>();

//Loop Through all records in the Trigger.new Collection

For(TSG__c T: Trigger.new)
{
    ss.add(T.email_address__c);
    aa.add(T.P21_CompanyCustomer_ID__c);
}


//Get User Info
TheUser = [Select ID,email from User where email IN:ss];
//Get Account Info
TheAcct = [Select ID,P21_CompanyCustomer_ID__c from Account where P21_CompanyCustomer_ID__c IN:aa];

    System.debug('@@@@--'+TheUser.size());
   
//Check to Make sure a record was retuned  
if (!TheUser.isEmpty()) {

     //Loop Through the Trigger (New Records)

     For (TSG__c T: Trigger.new) {
    
             For (Account acct: TheAcct) {
            
             For (User email: TheUser) {
        
             if (t.email_address__c == email.email && T.P21_CompanyCustomer_ID__c ==acct.P21_CompanyCustomer_ID__c) { //Make sure we match on email_address__c
            
                 //Insert into Account Team Here;
                
                    AccountTeamMember ca = new AccountTeamMember();
                    ca.AccountId = acct.Id;
                    ca.TeamMemberRole = 'Technical Sales';
                    ca.UserId = email.Id;
                    acctMembers.add(ca);
                   
                //Insert into Account Share Here;
               
                AccountShare caSharingRule = new AccountShare();
                    caSharingRule.AccountId = acct.Id;
                    caSharingRule.OpportunityAccessLevel = 'Edit';
                    caSharingRule.CaseAccessLevel = 'Edit';
                    caSharingRule.AccountAccessLevel = 'Edit';
                    caSharingRule.UserOrGroupId = email.Id;
                    acctSharingRules.add(caSharingRule);
                

                
                             }

                        }

                    }

                }

  
                     upsert acctMembers;
                    upsert acctSharingRules;    //This is what is causing the error.         
    
                
             
            }
        }


--Class--
/**
This is a Class for the auto adding account team based on TSG Group
*/

@isTest

Private class add_team {

Private static testmethod void myTeamTest(){

List<AccountTeamMember> acctMembers = new List<AccountTeamMember>();

List<AccountShare> acctSharingRules = new List<AccountShare>();


//Hold SalesRep
Set <String> ss = New Set<String>();
//Hold Customer ID
Set <String> aa = New Set<String>();
List<User> TheUser=new LIST<User>();
//Hold Account Info
List<Account> TheAcct=new LIST<Account>();
List<TSG__c> TheTSG = new List<TSG__c>();

  
  
       // Create the Acounts
    //Links to TSG P21 Customer ID
        List<Account> accList = new List<Account>();
        for (Integer i = 0; i < 1; i++) {
            Account newAcc = new Account(Name='test' + i,P21_CompanyCustomer_ID__c = '1-10009' + i );
            accList.add(newAcc);
        }
        insert accList;
       
      // create the Users
        List<User> userList = new List<User>();
        for (Integer i = 0; i< 200; i++) {
            USer newUser = new User(lastname = 'Test',Alias = 'Test',TimeZoneSidKey = 'GMT',
            LocaleSidKey = 'eu_ES',EmailEncodingKey = 'ISO-8859-1',
            ProfileId = '00ei0000000TYak',LanguageLocaleKey = 'en_US',
            userName='test' + i + '@tri-ed.com',email='test' + i + '@tri-ed.com');
            userList.add(newUser);
        }
        insert userList;
       
    //Create the TSG Records
    List<TSG__c> tsgList = new List<TSG__c>();
    For (Integer i = 0; i < 1; i++) {
        TSG__c newTSG = new TSG__c(Name = 'Test' + i,P21_CompanyCustomer_ID__c = accList[i].P21_CompanyCustomer_ID__c,email_address__c = 'jrosser@tri-ed.com');
       
        tsgList.add(newTSG);
      }
      insert tsgList;
   
   //     Try{
   //     update tsgList;
       
        
For(TSG__c tsg: tsgList) {
     ss.add(tsg.email_address__c);
     aa.add(tsg.P21_companycustomer_id__c);
     }
    
 
  //Get User Info
TheUser = [Select ID,email from User where email IN:ss];
//Get Account Info
TheAcct = [Select ID,P21_CompanyCustomer_ID__c from Account where P21_CompanyCustomer_ID__c IN:aa];
//
TheTSG = [Select ID,P21_companyCustomer_ID__c,email_address__c from TSG__C where P21_companyCustomer_ID__c IN:aa];

       
        IF(!TheAcct.isEmpty()) {
       
           
            //Loop Through the Trigger (New Records)
           
            For(TSG__c tsg2: TheTSG) {
           
             For (Account acct: TheAcct) { For (User email: TheUser) {
                
                
                
               if (tsg2.email_address__c == email.email && tsg2.P21_CompanyCustomer_ID__c == acct.P21_CompanyCustomer_ID__c) { //Make sure we match on email_address__c
                
                    AccountTeamMember ca = new AccountTeamMember();
                    ca.AccountId = acct.ID;
                    ca.TeamMemberRole = 'Technical Sales';
                    ca.UserId = email.ID;
                    acctMembers.add(ca);
                   
           //Insert into Account Share Here;
               
                AccountShare caSharingRule = new AccountShare();
                    caSharingRule.AccountId = acct.Id;
                    caSharingRule.OpportunityAccessLevel = 'Edit';
                    caSharingRule.CaseAccessLevel = 'Edit';
                    caSharingRule.AccountAccessLevel = 'Edit';
                    caSharingRule.UserOrGroupId = email.Id;
                    acctSharingRules.add(caSharingRule);
                
                   
                   
                            }
                         }
                       }
                     }
      
           
         }
        
        

                upsert acctMembers;
               upsert acctSharingRules; // This is what is causing the error
               
        
                
            
            }   

            }