ZTE Max Pro bonded with T-Mobile is receiving a firmware update today in US. The update comes as build TMO_Z981V1.0.0B13 that installs, March security patch along multiple improvements in overall firmware to improve stability and additional bug fixes. The update also addresses the VoLTE E911 timer issue that was observed in the previous update.
The update rolls out via OTA as we speak depending on the regional delay you’ll get the OTA knock at your device anytime soon. If you think the update is not hitting your device, go to Settings > About device > System updates. Check for System updates if available but before installing the update charge your battery well to avoid shutdown during the process.