Try to power off and reset your antminer maybe its just glitch or bug .. and try again..  If its not working
The other way that i know is firmware corrupted and reflashing firmware would be the solution..But i don't think is it allow to reflash your antminer since its still under warranty..
Better to contact the support from bitmain and ask if it can't avoid your warranty while flashing and ask to guide you.. .

Also check this guide for trouble shooting do this first to know if what problem of your hardware.
https://support.bitmain.com/hc/en-us/articles/220872007-Possible-problems-for-Antminer-Troubleshooting-for-S7-S9-L3-