Are you subscribed to Microsoft 365? The new iPad has a 10.2 inch screen and Microsoft requires a subscription to create or edit documents on screens10.1 inches or larger. See the following from https://apps.apple.com/us/app/microsoft-excel/id586683407
To create or edit documents, sign in with a free Microsoft account on devices with a screen size smaller than 10.1 inches.
Unlock the full Microsoft Office experience with a qualifying Microsoft 365 subscription for your phone, tablet, PC, and Mac.
Monthly Microsoft 365 subscriptions purchased from the app will be charged to your App Store account and will automatically renew within 24 hours prior to the end of the current subscription period unless auto-renewal is disabled beforehand. You can manage your subscriptions in your App Store account settings.