Mistake lease with $0/mo , can i get my tenant to pay?

[Reed Mollins]

so, i use an e-payment system, and last summer it generated a $0 lease and sent it to the tenant. That was dumb. But what was worse is that when it came back to my office, my person signed it too! but i'm not done. After that we didn't bill the tenant for 11 months, and now we finally caught it.

The lease is fully legally countersigned by my team.... what is my recourse ?!?!