Tell us what you are trying to do?
I just upgraded to 5.5 and of my two custom content types, one is fine and the other displays no results (it had 5 results before the update.
Is there any documentation that you are following?
Is there a similar example that we can see? versteckter Link
I'd be surprised if WordPress 5.5 changed the results of a query, and I'd like to take a look to see if I can spot what's happening.
Let me mark your next reply as private so that I can get log-in credentials from you—you may want to create a temporary admin user for me to use that you can later delete. And be sure to have a current backup of your site.
Can you confirm where I should be looking to see the problem? How are you trying to display the content?
I'm not sure what the history is here of editing the site, but when I edit the page which has the View, you can see in the screenshot how the Content Selection has nothing checked, so no post type is being queried by the View. Hence why you are not seeing any results.
I added the King Fu Schools post type and resaved the page, and it looks to be working now, if you can please confirm.