Nextcloud iOS app on iPad Pro won't preview a pdf file

I have a customer with a nextcloud server running 13.0.6

iOS version is current for October 2018.

They have several iOs devices including an iPad Pro. When attempting to browse pdf files on the iPad Pro the preview is not working. When a pdf file is tapped on it pulls up the menu asking what to open it with. Same file on the customers iPhone previews the file. We would like the preview function to work as it’s a much faster way to see the contents of the file. Does anyone know if there a setting or something that would cause this functionality?