Hi, may I ask what version of NA and NNMi you are running?  Do you have multiple NNMi servers (active / standby) and if so, were they failed over recently?  Or similar with NA, are you HS?  

You say that the nodes from NNMi have come across and are now in NA?  

Can you pick a device that was added by NNMi (or has an association with NNMi) and click on the Node UUID link (bottom of device home page) - does this bring you to NNMi and the node in question?  

 Can you check in NA -> Admin / Event Notification & Response Rules, if you sort by Action so the arrow is pointing down, do you have a number of NA / NNMi Integration rules?  

I'm not aware of that file, and do not have one on any of our systems.  Have you taken a look at it to ensure that it exists and check to see if you see any formatting issues?  

By chance, could a password for the account (NNMi and / or NA) have expired or certs expired or something similar?  If this is a new setup, then that may be unlikely, but wanted to rule it out. 

You could download the troubleshoot.zip file (Admin / Troubleshooting / Download Troubleshooting Information) .  On the form, for wrapper logs, enter 20 and then download the file.  In that zip, look through the appserver_wrapper.log files and see if you see a reference to a problem with the integration (or best case, you may find when this started and see a cause).  I've listed this last as it will be rather frustrating to sift through 20 files, each rather long and full of information not related to this issue, but still, may be contain useful information.  

Hopefully this will help,

Chris