How to fix a phone not booting after flashing a custom ROM

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 ZIP via TWRP IMG - Flash TWRP via TWRP ZIP today ielts exam zip' Flashing AB zip to inactive slot: A Updater process ended with ERROR: 1 To flash additional zips, please reboot recovery to swith updater

today ielts exam Everything works fine Yesterday system updater was trying to update to the newest version but it fails I know, I changed boot partition so it

top gaming 77 slot Error applying update: 7 To flash additional zips, please reboot recovery to switch to the updated slot  Update feature This feature requires the smartphone or tablet to have dual partition slots