device unlock process not working

Good morning user_4usyjv,

The most common misunderstanding is that the account has to also be at zero balance to unlock. This is not just about the phone balance, to unlock the device, the account has to also have zero balance. 

Here are the other unlock requirements to be aware of:

• At least 60 days must pass since your phone was activated.
• Your Xfinity Mobile account cannot have a past-due balance.
• Your phone cannot be reported lost, stolen or involved in fraudulent activity.

https://www.xfinity.com/support/articles/eligible-to-unlock-phone