How to prevent Excel for iOS from signing out of OneDrive?

Hi.

When attempting to open a file from OneDrive, Excel prompts for the login credentials even though I’ve entered them multiple times on past days. This behaviour repeats after perhaps a couple of days have passed since the last login. Is there a way to keep Excel logged in to OneDrive? This issue doesn’t occur with other apps I’m using (OneDrive, OneNote, Outlook or Office Lens).

I’m on an Office 365 Home Premium subscription. The device in use is an iPhone 6 with the latest updates.

Thank you for your help.

— Marko Kettunen