Your stream probably doesn’t contain any data. Check your stream condition. If you want to put all messages from palo alto firewall to stream, you can create static field in System - Inputs - click More actions - Add static field, for example Field name: paloalto, Field value: 1. Then use this field in Palo alto stream condition.
It’s not necessary to use stream for dashboard, you can also use another search condition, that will extract palo alto logs and then create dashboard.