Be aware of the behavior the folders cannot be opened through the browser via iPad.
I would like to inform you that the folder cannot be opened by tapping the screen via the Safari browser, even though the selected mark is ticked to the folder in the list display. So that, I am required to tap the gap space between the item and the folder for opening the folder.
This behavior have never been occurred before, however, I have difficulty using the iPad to view the files or access to OneDrive for Business at the present time. I hope the feature will be implemented to open the file by the tapping on the appropriate point by iPad.
We have had to force our tenant to use classic mode for Onedrive to enable it to work successfully on an iPad browser. Support were not interested into looking into the issue, just suggested that I post here.