Can you show the full contents of
REDIS = {
...
}
from your /opt/netbox/netbox/netbox/configuration.py ?
"Client sent AUTH, but no password is set" suggests you have set a password here, but you shouldn't do (because the redis server isn't expecting one)
If redis is running on the same server as netbox, then this section can be copied exactly as-is from
configuration.example.py