Networker 8.2.4 Administrator and Root Accounts are Restricted

Hello,

We are currently having trouble logging into the NMC. We get the following message when attempting to log in with either the administrator or root account: "The specified user name is restricted and cannot be used to log into the system". Everything had been working well and from one week to the next we began to get this message.

I've looked up online on how to un-restrict user accounts but they all tell me I have to log into the NMC as an administrator. 

We've looked at the logs and cannot find anything relevant to the message we are receiving. Does anyone have any pointers as to where to look or a workaround to un-restrict the administrator and root accounts? 

Thanks in advance.