I can't get the iPad update to download

You are not the Original Poster here.

Your iPad year and model are different.

If you actually have a 2014 iPad Air 2 still operating under iOS 12.4, your iPad is waaaay too far behind in iOS/iPadOS upgrades/updates.

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, or later macOS, 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 model, using the iTunes Software Update feature, to its current, maximum OS of iOS 12.5.5/iPadOS 15.2.

Make sure your iPad is, at least, charged to 50% or greater to attempt this.

Also, make sure your iPad has, at least, between 6-8 GBs of free internal data storage space for downloading and installing a major iOS/iPadOS upgrade.

Make sure your desktop/laptop computer has plenty of internal drive storage space, also.

Also, make sure to do a backup of your iPad's data, prior to upgrading/updating.

Backup to Apple iCloud and/or a full Mac or Windows PC using the same iTunes app OR, if a newer Mac running macOS Catalina, or later, making a backup using the macOS Finder app.

If NO access to a Mac or Windows computer, you will have to seek help from a good friend or family member, with a full Mac or Windows PC, to help you out

OR

Search online to locate and call contact your nearest, “local” Apple Store location to try/attempt to make an appointment to get your Apple iPad upgraded/updated to its latest iPadOS 15 version.

Apple Store employees will be glad to help/assist you.

If your iPad Air model is actually a 2013 iPad Air 1st gen, then iOS 12.5.5 is the farthest that year and model can update to, as it is too old to upgrade to newer any version of iPadOS and therefore cannot be patched for the latest security vulnerability.

Best of Luck to You!

Possibly your iPad is too old to upgrade/update?

It is a little hard to help/advise you when you provide little to NO useful information about your iPad.

Here are my questions to you.

Can you, please, confirm what year and model iPad do you have/own?

The “A” model number can be found on the aluminium back of your iPad, in very small print, right under the larger bold print “iPad” on the back of the iPad.

What iOS/iPadOS version is this iPad, currently, running?

What is the rated, internal data storage space/capacity of your iPad model and how much of this free, internal data storage capacity is left inside of your iPad model?

All of that additional info can be found in the Settings app, General settings panel, About.

Please try to make an attempt to answer all questions asked.

Thank You.

I have iPad Air 2 running 12.4.1. I can download 15.6.1, but I cannot install it. The update should support Air 2? Any help would be grateful.

Thank you very much. I went through iTunes on my PC and and worked great. Normally a PC user and it is my Mom's iPad so she will be thrilled.

Thanks Again!