You say you have put " conditions" but what you want aren't all conditions. That might just be how you've phrased it but I think you need:
Assignment: Specific user included (userx@microsoft.com)
Target Resources: Include all cloud apps, exclude App X
Grant: Block Access
Have you tried looking at the logs when the user logs in? You should be able to see exactly which conditional access policy rules get triggered and how access is being granted.
The logs are available in the portal in Conditional Access under monitoring and you can filter to a particular user. Click the entry for a details pane.
Hope this helps