Yes, you can refund it. Orders shipped outside the EU have a 60-day return window, counted from the delivery date, so five weeks is well inside it 1.

• The customer pays return shipping for non-EU orders, unless the item arrived damaged or wrong 1.
• Norway is treated as non-EU for returns, even though it is in the EEA 3.
• Refunds go back to the original payment method within 5 business days of the parcel arriving 1.

If the customer wants to keep things simple, the support macro “Non-EU return, refund approved” already covers the wording, including the customs note 2.