Repairing device after warranty replacement

[mijofa]

A friend of mine had their device die on them, so they went through the usual warranty process and got a replacement sent to them. They're all sorted with the new device now and happy with that.
Since they weren't asked to send back the old/dead device, and I haven't pulled apart any hardware in a while, I decided to have a crack at the old/dead device and see what was wrong with it.

I've got the old device turning on now (although I think the speaker's dead, and the water seal is compromised) but it can't be paired in the fitbit app due to being marked as stolen/replaced by Fitbit as part of the warranty process.
Is this device useless now and should just be thrown out, or is there a process I could go through to mark the hardware as refurbished after Fitbit gave up on it?

It's important that the replacement device not be disabled regardless, because I'm not confident this device is properly fixed anyway (I am not an expert at this) and my friend still needs their Fitbit.
If the answer is along the lines of "you bought one device, you only get one at a time" that's fine, I'll just throw this out and consider my attempt at repair to be a learning process and move on.

[Odyssey13]

Hi @mijofa pretty much once Fitbit has locked a device, it can't be set up again for someone to use it. It's nice to see you like to tinker with things, but there's no getting around this one.

[MarkMM]

@mijofa Are you getting a message in the app that the device is locked due to being replaced/stolen, or are you assuming? I never heard of or had a replaced device locked, and I'm not convinced Fitbit can remotely disable them, but there's always new technology. 

[mijofa]

@Odyssey13 bugger, suspected as much but was hoping otherwise. Thanks for confirming

[mijofa]

@MarkMM yes, when using the app to pair with the Fitbit the app says the "device has been locked and cannot be paired. This may happen if a device is reported lost or if a warranty replacement has been issued"

Makes sense though, they don't want people lying about warranty replacements to get an extra device, so they've disabled pairing with the old one.
Since the Fitbit's encryption syncs right up to the cloud with the app/phone not being able to handle pairing without the cloud it's real easy to disable them remotely.