can't select manual back up in iTunes for Windows

Hello,

I'm trying to manually back up my iPhone to iTunes. It's running 16.6.1 and it's the first that it's been connected to iTunes and the first time that I've tried to manually back it up.

When I connect to iTunes the only options available are automatic back to iCloud or automatic back up to this computer.

The manual back option is greyed out. See attached image.

Additionally, although the automatic back up to this computer is selected it doesn't back up.

I've just manually backed up my iPad and that went as normal.