Unable to mount data or system error

How to fix a phone not booting after flashing a custom ROM to flash additional zips please reboot recovery to switch to the update slot And if it is going , then simply flash the stock rom zip file through custom recovery by wiping cache etc top ganapati online slot sites And if it is going , then simply flash the stock rom zip file through custom recovery by wiping cache etc

toto slot zip to inactive slot: B Devices on super may not mount until rebooting recovery To flash additional zip please reboot recovery to switch to the update slot