Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Are you trying to install from a web download instead of the App Store, and does the app show a spinning circle or say Waiting on the Home screen? Also, how much free storage is available on your iPad?
On an iPad, Microsoft 365 does not install from a downloaded installer like on a PC or Mac. It must be installed directly from the Apple App Store. Please open the App Store, search for Microsoft 365, and tap Get or Install. If it appears stuck, try restarting the iPad, signing out and back into the App Store, and confirming you have enough free storage. You can also try installing individual apps like Word or Excel, which automatically activate with your Microsoft account. https://support.microsoft.com/en-gb/office/set-up-the-office-app-and-outlook-on-ios-devices-0402b37e-49c4-4419-a030-f34c2013041f.
If the app downloads but will not finish installing, Apple ID or network issues are often the cause. https://support.microsoft.com/en-us/office/troubleshoot-installing-office-35ff2def-e0b2-4dac-9784-4cf212c1f6c2.