Selenium - wait for report generation

Question

Part of what I am trying to automate are:

1. Go to : this
2. Pick "25" from the Page Size dropdown list (a required selection for generating the report).
3. Click the View Report button.
4. Wait for the report to be produced.
5. Click the Save/Export button and select the CSV option.

However, how can I set a condition that can detect whether the report is generated? There are 2 possible transitions from step 4 to step 5 - Loading or just Blank (which I have no idea why):

Here is the test case that failed:

This is my first time using Selenium, and I am planning to export this to work with C#.

Thank you!