Your husband's iPhone must participate in the Apple's Find My Network, in order for it to relay your AirTag's information to the Apple servers. To do so, the following needs to be enabled on his phone:
• Find My: Settings > Apple ID > Find My > Find My iPhone > Find My iPhone
• Find My Network: Settings > Apple ID > Find My iPhone > Find My network
• Location Services: Settings > Privacy & Security > Location Services > Location Services
• Bluetooth: Settings > Bluetooth > Bluetooth
His phone must also have an active Internet connection, either via a cellular or Wi-Fi connection.