Used Apple Watch - Removed from former iCloud, but still says it's attached
I bought a used Apple Watch. The former owner unpaired it and reset it, but didn't remove it from his iCloud account until after I received it. He logged in and remotely removed it, but when I try and set it up it still says "This Apple Watch is linked to an Apple ID. Enter the Apple ID and password that were used to setup this Apple Watch."
I've checked the serial number here and it properly shows activation lock is off: https://www.icloud.com/activationlock/
I've tried resetting it, to no avail. What more can I do? Does the Apple watch need to have a connection to "realize" it's no longer associated with that Apple ID? And if so, how?