I’m unable to install iOS 14.3 on my iPad Air 2. I’ve tried deleting the update and download/install but I’m still getting an error message...

If you have access to a full computer, like a Mac or Windows PC, try either using the Finder on a Mac that has the newest macOS Catalina installed OR with an older Mac with an older Mac OS, download and install the latest iTunes version ( or latest iTunes for Windows PC ), make sure the Mac or Windows PC is connected to the Internet, connect your iPad by the USB charge cable to the computer and let the iTunes application upgrade/update that iPad Air 2 model, using the iTunes Software Update feature, to its current, maximum iPadOS 14.3

Best of Luck to You!

How old is this MacBook Pro?

What is the MacOS version tbis MacBook Pro is currently running?

What year is this MacBook Pro.

Also, your iTunes version IS out of date!

I am trying to ascertain whether that old MacBook Pro can have its MacOS updated and make it possible to update your iTunes version to, at least, iTunes version 12.6.5.3 or 12.8.x.

Also, what is the exact iOS/iPadOS version is your iPad Air 2 currently running?