R9000 not allowing some wired devices to connect

My R9000 has been working great for months but over the last 2 days all of my Sonos devices (all hard wired to the network) have stopped working.  Nothing about my configuration has changed - no R9000 firmware updates - these devices have all stopped working.  They show up under the Netgear Admin Portal / Advanced / Security / Access Control list of "allowed devices not currently connected to the network" - yet none of them are connected.  I removed all of them from this list and then unplugged / restarted each device  - they slowly start appreaing on this "not connected" list which tells me the R9000 gives them a DHCP address but for some reason they aren't connecting.  They are the only devices that aren't connected - all other wired devices work.  Maybe this is a Sonos thing?