Just verified, the same issue, it seems that you need to update your device from 13.6.1 to 13.7, feel like 13.6.1 is just a defective version.
I was trying to deploy the app from Xcode 11.7 to a few devices that are running iOS 11.6.1. Then I got this error
Error: "<DeviceName> is not available. Please reconnect the device." I tried the method suggested by @JiminyKirket by setting my deployment target to 13.0, 13.6 but there is no luck for me
Then I upgraded all my devices to iOS 11.7 and the problem is resolved.
I have no idea what happened, but it's quite suspicious that Xcode 11.6 and Xcode 11.7 are released only 4 days apart from each other.