I'm afraid I won't be able to help you further on this one. I have no experience with that device. While this is not a Meraki problem but rather a Linksys problem, someone else on here may be able to provide some hints or troubleshooting steps.
Your issue might be because that adapter is old and doesn't support 802.11ac from the looks of it. You'll want to have a 3-stream 802.11ac adapter to make sure your able to actually decode all frames, otherwise, you'll just see management frames instead of data.