I just bought a retuned u200 lock from a online store here in Sweden and can’t add the lock to my Aqara home.
When I scan the Aqara code in the app it thinks for about a minute then “can’t find unit”.
It connects to my Apple home via Matter without issues… but not Aqara home.
I’m thinking it might be due to the previous owner not removing it from its Aqara account?
Hi there, it looks like you’re experiencing a support-related issue. We’ve automatically created a support ticket for you and will reach out via the forum email within the next two business days.
If other members have any suggestions or insights on this topic, feel free to share!
Hi!
I found this post in another thread: U200 - secondhand unlock - #8 by calusbalus
If that doesn’t help, Aqara Support will be able to assist you.
Since i don’t have the admin code I guess I’ll have to wait for Aqara support 
Hi, try this method. Be sure to untie the HomeKit first. Factory Reset Smart Lock U200 - Matter code method