This means that the index to the database is currently rebuilding and you will not be able to login using nitroview.
This is typically caused by the device not being powered down correctly or after a recent upgrade.
When this happens the index must be rebuilt, before the data base is accessible again.
This process can take up to several hours to complete.
If more than 4 hours has passed and the error persists please contact support.
You can also restart the ESM services if it is taking too long. We faced this issue some times and restarting the services solved the problem.