Hi PeterJal
On tablets, if your screen size is larger than 10.1 inches, you must have a licence to subscribe to Microsoft 365 Personal or Family under your account in order to use it.Otherwise you will be shown as not having a subscription to use it.
So if you want to use Office apps on your iPad Air (5gen), you need to have a paid subscription to use them.
On the iPad Mini (A17 Pro) you can use it for free as per the instructions and we recommend you try again with a new Microsoft account.
Unfortunately, we've been getting feedback since last year that Office doesn't activate properly on the iPad Mini, so if you're still unable to activate it with a different Microsoft account, then you're affected by this hotspot issue.
Would you like to consider a free one-month trial of Microsoft 365?
Or you can try the Office web side to handle your work temporarily, and you can try Office for free on the web side.
Free Trial - Try Microsoft 365 for a month - Microsoft Store
Best Regards,
LucyW-MSFT | Microsoft Community Support Specialist