Question Unity navmesh agent don't work

so i got this problem before but i forgot how i fixed it so yaa I'm here so i was using unity nav mesh ageent component it was working fine i closed unity opened it next day change they terrain baked the terrain from the navigation window placed my zombie ai and it wasn't working to check if it was my terrain issue i created a blank new terrain baked it and tested again but my zombie ai wasn't working again but i disabled the navmesh agent component from my zombie and enabled it again it started working now idk how to fix this it's definitely not the script issue cuz im using standard asset default ai script plz help

 

Without more specific information no one can help you with this I'm afraid.