Try pairing the remote again. Unplug the power from the (I assume Express) 4k+ and find the pairing button inside the battery compartment of the remote. Press and hold the button until the green light starts flashing and then plug in the power to the Express. Set the remote down next to the Express and it will hopefully pair once it finishes booting.
By the way, the remote you got should also work with your Stick, but you have to pair it.
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