iTunes still showing IOS 17.7.2 as latest iPad update

I am trying to update my 8th generation IPad to 18.3. Despite off loading all my apps the update file is so large that it maintains not enough space after initial download prior to trying to install.

i have tried to update via iTunes but when I check for updates it keeps saying that it is up to date on 17.7.2.

Apple please sort out this out. You have had 3 updates since 17.7.2. and none of them have shown up on iTunes. Before you ask yes my iTunes app is on the latest iteration according to your systems