123TRB,
Thanks for following up. Let's grab more information about what's going on, so we can figure this out.
How you are attempting to use your new iPad Air with Keynote Remote. To elaborate further on that question, here are some examples of how you can use it: Use a remote to control a Keynote presentation - Apple Support. Do any of these options work, or, do they all fail to work properly with your new iPad Air? At which point in the steps, does it fail? i.e. you never see the Set Up Remote screen, device doesn't appear after turning on Enable Remotes, never receive four-digit code or doesn't match, etc. As quoted from this article, "Note: The old Keynote Remote app previously available from the App Store is no longer supported."
Also, there was a new iPadOS released while we were in discussion. Consider trying to update your iPadOS to see if this helps improve your experience with Keynote Remote: Update your iPhone, iPad, or iPod touch - Apple Support.
We look forward to hearing back from you.