Why is my iPad not updating to the newest version

Are you trying to update to iOS 14, using your computer or Wi-Fi?

Update your iPhone, iPad, or iPod touch - Apple Support

If this is a first generation iPad Air, iOS 12.4.8 is the latest update for this model.

The original “first generation” iPad Air cannot be updated to iPadOS 13.x as it lacks the necessary minimum CPU/RAM specification to support iPadOS.

Major update support for iPad Air ended in September 2019; the final supported version of iOS for the Air1 being iOS 12.4.8. If you have already updated to the iOS 12.4.8, you definitely have an Air1.

If however you have an iPad Air2, or Air3, then you should be able to update to iPadOS 14.0.1. As these models were upgradable to iPadOS 13.x, whose release precedes the final iOS 12.4.8 release, the final iOS 12.x releases will not be found on either Air2 or Air3 models.

As such, with an iPad Air1 it cannot be updated further. If Apps that you need require iPadOS 13/14, then you have no alternative other than to replace your iPad with a newer model.

Sorry, this is perhaps not the news that you were hoping to hear, but I hope this information is helpful in informing your options.