Run-time error'70' : Permission denied with ComboBox_Change()

I have two ComboBoxes in Excel (ContractTypeComboBox & PositionComboBox), and I need the 2nd ComboBox (PositionComboBox) to populate dynamically based on each of the selection in the 1st ComboBox (ContractTypeComboBox), which is based on a table I have setup on another worksheet (Tables).

However, I keep getting the "Run-time error'70' : Permission denied.", when selecting any of the options in the ContractTypeComboBox.

Please can somebody help. I have pasted the code below :

Option Explicit


Private Sub ContractTypeComboBox_Change()
      
        
    Dim FixedTermContract As Range
    Dim FixedTermContractTTO As Range
    Dim Permanent As Range
    Dim PermanentTTO As Range
    Dim SupportWorker As Range
    Dim Trainee As Range

    Dim wbNurseryNewEmployeeForm As Workbook

    Dim wsNewForm As Worksheet
    Dim wsNNEFTables As Worksheet
  
  
    ' Set this Workbook's name.
    Set wbNurseryNewEmployeeForm = ActiveWorkbook


    ' Set Worksheet name(s).
    Set wsNewForm = wbNurseryNewEmployeeForm.Worksheets("New Form")
    Set wsNNEFTables = wbNurseryNewEmployeeForm.Worksheets("Tables")
  
    
    ' Populate the Position ComboBox drop-down list.
    If wsNewForm.Range("ContractType").Value = "Permanent" Then
    
       For Each Permanent In wsNNEFTables.Range("Permanents")
       
                PositionComboBox.AddItem Permanent.Offset(0, -1).Value
    
       Next Permanent
    
    End If

    If wsNewForm.Range("ContractType").Value = "Permanent (TTO)" Then
    
       For Each PermanentTTO In wsNNEFTables.Range("PermanentsTTO")
       
                PositionComboBox.AddItem PermanentTTO.Offset(0, -2).Value
    
       Next PermanentTTO
    
    End If

    If wsNewForm.Range("ContractType").Value = "Support Worker" Then
    
       For Each SupportWorker In wsNNEFTables.Range("SupportWorkers")
       
                PositionComboBox.AddItem SupportWorker.Offset(0, -3).Value
    
       Next SupportWorker
    
    End If
    
    If wsNewForm.Range("ContractType").Value = "Fixed Term Contract" Then
    
       For Each FixedTermContract In wsNNEFTables.Range("FixedTermContracts")
       
                PositionComboBox.AddItem FixedTermContract.Offset(0, -4).Value
    
       Next FixedTermContract
    
    End If
    
    If wsNewForm.Range("ContractType").Value = "Fixed Term Contract (TTO)" Then
    
       For Each FixedTermContractTTO In wsNNEFTables.Range("FixedTermContractsTTO")
       
                PositionComboBox.AddItem FixedTermContractTTO.Offset(0, -5).Value
    
       Next FixedTermContractTTO
    
    End If

    If wsNewForm.Range("ContractType").Value = "Trainee" Then
    
       For Each Trainee In wsNNEFTables.Range("Trainees")
       
                PositionComboBox.AddItem Trainee.Offset(0, -6).Value
    
       Next Trainee
    
    End If
    

End Sub