I received batt_deep_discharge status in app

I replace the battery in my robot for 4 months ago and today the robot was off. I tuned it on, the battery led was blinking red and the app displayed an error message: batt_deep_discharge

Any suggestions about how to fix this?

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 0
crwdns2934285:0crwdne2934285:0