Asus had some issues with the servers during the last 48 or so hours.I had the exact same error last night when trying to unlock the first time. I must have tried about 4-5 times every time with the same message.
After an hour or 2 i tried again and then it worked immediately. Might have been lucky that the servers were working at that time and maybe had nothing to do with the battery...
Don't know if it can help, but the first time i tried it must have been around 8pm GMT, second time it was 10pm GMT.
And ripping the actual unlocker app apart (oops, sorry asus) told me it connects to https://mdm.asus.com/ .
This made me laugh, as when you open that page, you'll see
I'm not sure what to think of that...It works !
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