Clicking on the configure link gives the message “Z-Wave JS: Retrying setup”, “Failed to connect: Cannot connect to host …..” as in the example below.

2. Cause

Possible causes based on my own experience:

changing the Z-Wave controller from USB port on the Raspberry Pi 4;
a Home Assistant update;
moving the SD-card with Home Assistant to another Raspberry Pi 4.

3. Solution

The next sections describe how to fix the Home Assistant Z-Wave connection issue due to a change in USB port ID to which the Z-Wave controller is attached.

3.1 Quick steps

The quick steps below are for the experienced Home Assistant user. Less experienced users are recommended to skip this section and follow the detailed steps in section 3.2.

Find out the correct USB port off the Z-Wave controller
In the Home Assistant sidebar select Z-Wave JS
Click on the hamburger menu in the top left of the Z-Wave JS control panel and select settings.
Open the Z-Wave section
Change the USB port under Serial Port to the correct port.
Save the new settings by clicking on save in the lower right.
Check Z-Wave is working again.

3.2 Detailed steps

The steps below describe in detail how to fix the Home Assistant Z-Wave connection caused by a change in USB port ID registered for the Z-Wave controller.

Find out the correct USB port by opening the Hardware menu under Settings > System > Hardware.
Click on the 3 dots in the upper right and select “All” from the menu.
Type “tty” in the search box and remember the port ID of the Z-Wave controller. I am using the Aeotec Z-Stick 7 Z-wave controller, which is using the Z-Wave chip from Silicon labs. So ttyUSB0 is in my case the correct port.
The ttyUSB1 port has my Plugwise stick inserted.
In the Home Assistant sidebar select Z-Wave JS
The control panel for Z-Wave JS does not list any devices and shows a red error message similar as “Driver: Failed to initialize the driver: ZWave Error: Timeout while waiting for an ACK from the controller (ZW0100) at Driver…”
Click on the hamburger menu in the top left of the Z-Wave JS control panel
and select “Settings” from the menu
Open the Z-Wave section
Change the USB port under Serial Port to the correct port.
Save the new settings by clicking on save in the lower right.
The warning in the header of the Z-Wave JS control panel should have been disappeared.
When going back to Home Assistant settings > Devices & Services the Z-Wave JS integration might still show the warning. Click on the 3 dots and select Reload.
The Z-Wave JS integration warning should be disappeared.