You receive a "Sorry, there was a problem and we can't open this document" error when you try to view an Office document in Office Web Apps and the primary reason for the behaviour are the following settings
- AllowOAuthOverHttp setting is set to False (It should be set to True)
- The SharePoint host domain is not in the allow list. Use the New-OfficeWebAppsHost command to add the domain to the allow list
However, you might also see the same error when your OWA server is not able to communicate with the SharePoint server. Check that both SharePoint and the OWA server are able to communicate with each other.