You are maybe getting some issues while trying to connect Qobuz to Soundiiz.
Be sure to logout from Qobuz website before connecting Qobuz to Soundiiz. Go on https://www.qobuz.com/ and logout from your Qobuz account.
Once that done, go back on Soundiiz, select "Qobuz" and enter your Qobuz credentials. You will get a success Qobuz message after that and the popup will be closed by itself.
That should be good ! If you want to use another Qobuz account, be sure to disconnect it from Soundiiz and again, logout from Qobuz website first. Then go back to Soundiiz and repeat these steps.
If you are not seeing any Qobuz login interface, be sure to have allowed popups in your browser.