ipad m3 air to macbook air failing backup

ipad m3 air backup failing.

iPad iOS 26.2 plus mac 26.2.

I backup my iPad air m3 (and previous iPads) every week to my mac computer m4 mac book air.

I am now getting this message when i try to backup iPad.

However there is no iPad backup on my mac.

There is only iPhone backup.

I did delete that just in case.

I have restarted both mac & iPad but same problem.

any ideas ?