Problem

This error occurs if the 3PAR host exists with the correct host name
that the OpenStack Block Storage drivers expect but the volume was
created in a different domain.

HTTPNotFound: Not found (HTTP 404) NON_EXISTENT_VLUN - VLUN 'osv-DqT7CE3mSrWi4gZJmHAP-Q' was not found.

Solution

The hpe3par_domain configuration items either need to be
updated to use the domain the 3PAR host currently resides in, or the
3PAR host needs to be moved to the domain that the volume was created
in.