WD Discovery trouble

I’ve downloaded and installed the WD Discovery app on a Mac running El Capitan 10.11.6.
The installation was a success.

The app icon appears on the top bar as expected.

But when I click on it the only screen that appears is the app screen but I can’t scroll down or select an app.
The app menu doesn’t appear nor the log in / storage screen.

I’ve uninstalled and re-installed but the problem continues.

It’s possible there’s a macOS firewall or network router or firewall blocking access to the mycloud.com online servers. Have you connected the mac to a different network?

The firewall is off.
I have 2 other iMacs connected to the same network and with the WD Discovery working just fine…

This is what happens (in the image).
It just freezes there.