There could be several reasons why your NetID is not working.
First, there is sometimes a 24-hour turnaround with newly activated NetIDs.
Second, all UNR NetID passwords have to be changed once a year. If you are being offered the "new" box, you should be able to go ahead and create a new password right there. If not, you will need to go the NetID Password Reset page: http://www.unr.edu/it/login-ids/netid/netid-password-reset
Note: If you have other devices that automatically query your NetID (example: smart phone that connects to your UNR email) you may need to shut them down, then bring them back up and change the password on each. Otherwise, systems that keep querying with the old password could lock up your account (multiple tries with the wrong password lock the account for 30 minutes).
Here are some NetID troubleshooting tips you can also try: http://www.unr.edu/it/login-ids/netid/netid-troubleshooting
If you continue to have problems with your NetID, contact the Computing Help Desk at 682-5000 so they can check the status of your account.