Backup Now greyed out in iTunes

Trying to update my iPhone 14 to the latest iOS but want to back it up first to my PC. When connected to my Win10 PC the Backup Now button is greyed out (as is the Backup to iCloud option). I know my PC is up to date and I've checked for iTunes updates and I'm running the latest version. I had no problems when I backed up my phone about 8 weeks ago. I've reviewed other topics on this subject within this forum and can't see any reason why I am now unable to perform a bckup.