ERROR: ORA-01033: ORACLE initialization or shutdown in progress

hi, all

when it came to connecting to the instances of the databases using the SCAN (Single Client Access Name),

we had the error

ERROR: ORA-01033: ORACLE initialization or shutdown in progress

it was not possible to connect to any of the databases configured in the RAC.

To reset the service, the scan and local listener service was restarted.

We checked the logs of the listener, to determine what was the reason of the block but was not found nothing that could indicate what was the problem so that we can not access the databases, we have reviewed several notes of the suport oracle, but we did not find what was the real cause of the blocking of the databases.