It should work (see this discussion), but I suggest you make sure the Ethernet connection is still live by connecting another Ethernet device to it, and I also suggest you ensure both the originating Boost device, and the secondary one are connected to the same switch to test.
I have a similar set up where I have a mix of wired and wireless booster connections. Based on my experience, the booster seems to use wired over wireless automatically if the connection is available. I didn't have to do anything - one moment, it was wireless and the moment I connect to the Ethernet port, it became wired. Like the post above, perhaps, start with checking to make sure that the port is live (and connected to the main modem).