The backup button in the iPhone summary in iTunes is greyed out. I tried it with a different phone and it was still greyed out but it works as soon as I switch users. I Used an iPhone 8 iOS 14.3 and an iPhone 6 Plus iOS 12.5.1 on macOS 10.12.6. Updating iOS had no effect. Both devices had the same outcome until I switched users. is there a way to fix it so I don't have to keep switching users to backup my phone?