See the workarounds below if either one will work:
Workaround 1: When the node is set up with a managed switch as pictured below, your devices will not be able to connect to the child node’s WiFi unless the managed switch is configured to forward and allow VLAN 3 and VLAN 4 traffic on all ports connecting to a node. These two VLANs are needed for WiFi setup to function. No configuration is needed for unmanaged switches. To configure VLAN on your Linksys Managed switch, click here. If you have a Linksys Smart Switch, click here.
Workaround 2: When the node is set up with a managed switch as pictured above, turn OFF HomeKit Integration from the Linksys app and power cycle all child nodes. As a trade-off, you cannot link the node to the Apple® Home app. For complete instructions, follow the steps below:
Log in to the Linksys app. Then, tap the Menu icon at the upper-left corner of the screen and then tap Network Administration.
Turn OFF the HomeKit Integration button.