itune version is the current version, but update of ipados not taking place.

While downloading and installing of ipaOS 15.7.9 , after consuming lots of data, its failed two timed today. then I tried through iTunes connecting to my laptop, there I found new problem, a pop up comes to say to update the iTunes version to the latest one, but it is already the latest version. ultimately i am unable to update the new ipad os in my ipad . please help