When you have a lot of activities going on in your life, having one calendar may not be enough. For some people, they want to separate their work calendar from their personal calendar. Think of social events, class schedules or even family plans.
Managing different calendars is possible thanks to Outlook. Aside from the default calendar we see on the Microsoft app, we can also add other calendars or create new ones.

However, there seems to be an issue where a blank screen section appears on Outlook whenever you use multiple calendars. It should not be the case but it can be an error on the app.
Fix Outlook Calendar Showing Blank Screen Section when Switching Between Multiple Calendars
If you encounter the same problem with Outlook, there are ways you can try to troubleshoot it. Fortunately, Microsoft has looked into the issue and suggested a workaround.

One method is to clear the cache. On your Outlook, click on File and navigate to Options. Select Advanced and go to the Outlook start and exit section. There you can select Empty cache.
Another way is to close Outlook and relaunch it. But, you will need to properly end the task from the Task Manager. To do so, click the Start button and open the Task Manager. Look for Microsoft Outlook and select it. Click the End task button. Now, you can relaunch the app.
Scrolling the calendar view several times may also help. From your Calendar View, all you have to do is scroll the page up and down until you will see the blank section filled up. It may take some time, but it works for some users.
Lastly, set the Zoom settings to less than 100%. Go to View and select Zoom. Make sure to set it below 100%.
In Summary
There are several methods that will help you fix the blank sections on your Outlook Calendar. Work on them one at a time and see if it resolves the issue.