Used ADB to unlock bootloader but now ADB can't "see" the phone in download mode

I have a Windows 7 PC and I used that with Android SDK to unlock the bootloader and that worked. Now (trying to install recovery) I can put the phone (5.1.1) in download mode and the PC registers the phone in Device Manager but ADB doesn't see it. I've changed nothing with the PC since unlocking the bootloader and I've confirmed USB debugging is enabled on the phone but the command 'adb devices' lists nothing below 'List of Devices Attached'. Has anyone heard of this? Any troubleshooting suggestions?

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