I had the same problem, Admin needs to have a capital A to get in.
I Factory reset the printer, but still can't get in, either with admin - 1111 or admin - <Serial Number>
Now it says user locked out. Tempted to just pack printer up and return it.
I have a new C315. Has never printed a single page, never plugged into the network. I'm the only one who has ever touched this machine.
I'm trying to get network setup, but it keeps asking for username and password. During setup, I gave it the same password I use for my other 30 machines. I'm using "admin" as the login, but it never lets me in.
How do I fix this?