I was able to duplicate the issue described on this thread.
In my case the issue occurred on a Windows 10 64 bit os
What I did to resolve the iTunes issue was to uninstall iCloud Drive, but leave iTunes installed.
Immediately after uninstalling iCloud Drive iTunes began working again.
Since my hard drive is only 117 GB, I had previously deselected all checkmarks on the iCloud Drive app pertaining to what should be synced with the device. I highly suspect that I could have resolved the issue by selectively re-checking items in the iCloud drive. But, in my case, I don't really need iCloud Drive on the device. Uninstalling it was not a hardship.