You should always update the Adyen Inventory when removing a terminal from a store. First locate the serial number of the terminal on the back of the terminal e.g. 275-268-492.
Go to https://ca-live.adyen.com/ca/ca/postfm/showposterminals.shtml & select the merchant account of the store. You will se a list with terminals like below. Select the terminal you are removing & choose the reason for moving the terminal in the lower right corner.
You are required at all times to ensure that the terminal overview is up to date.
If you see a terminal that is either Offline or Reassign scheduled (inventory), this can indicate that the terminal was taken offline before the registration went through.