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 :

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It was originally populated using ListFillRange, which I have now removed. I have tried using

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before AddItem, but receive the following error message : "Run-time error '438' : Object doesn't support this property or method."

Yes, and with adding an IF statement within each of the For Each Loops to check if each cell in the range contains a certain value. An example is copied here for completeness :

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Thanks for your help!