From the screen you have shared of the network tab, it clearly indicates a connection error, if you expand the width of the second column, you will be able to see the complete error name given by chrome.
On my side I tried to curl to your server with the endpoint configured on your environment and it could not resolve the host. But this might be expected if you have set up a private company network.
I would suspect that your server is running in a protected network, which is why I wasn’t able to reach the specified apiEndpoint of your “Production AUS” environment.
If this issue is present for only one user and for this specific environment, it is most likely the case that this user has not enabled his VPN.
Can the affected user try to reach the {apiEndpoint}/forest of the “Production AUS” environment via curl or simply pasting the url in chrome directly ?
Like so (this example is done using our agent) :