I have the same/similar problem. Trying to register new Blackwidow keyboard and get "serial number is not known".

First character looks like either upper case i or lowercase L e.g. I or l neither work.

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JoeyIsAZN24
I have tried IO and io, neither have worked. What can I do?

try uppercase i then uppercase o as the first two characters of your serial number. I had same problem, thinking the second character was a zero, it weasn't.
Best of luck

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