I can connect to devices on my router when my laptop is connected to my Hub, but I can't do the reverse. Why not?

You have two local networks - one is created by your router, with IP addresses of something like 192.168.1.x, and one created by the Hub(s) with IP addresses of 101.x.y.z. (Note: this is NOT true with the AyrMesh Router - the Router and Hubs adjust their IP addresses and routing so they create one "large" 10.x.y.z network)

Because the Hubs are "downstream" of the router, they are "aware" of the Router's network, but the same isn't true in reverse - the router doesn't "know" about the Hub's network. So it tries to route any packets initiating in its network to the Internet instead of to the AyrMesh Router.

To force the router to route packets bound for the 101.x.y.z network to the Hubs, you have to set up a "static route" in the Linksys router to tell it where to send those packets. This is very simple on most routers (not on D-Link brand routers, unfortunately).

Attached are notes on how to do this (as well as turn off WiFi and set up IP address "reservations", as appropriate) in general and for several popular router makes.