itunes option to automatically sync is disabled (grayed out)
For years, I have been automatically syncing my iPhone with iTunes. When I plugged in the USB cable, iTunes started automatically and it immediately backed up and synced my phone. Now it refuses to do so and the iTunes option to automatically sync is disabled (grayed out). What is blocking this option?
Thank you.
iPhone 6, iOS 11.3.1, iTunes 12.7.4.80 running on Win 7