Most likely your partition table has 4 partitions. So either manully use sfdisk from ubiboot rescue mode or get your hands on internal flasher and run:

sudo flasher -O nand-repartition -f -F main.cbin -F emmc.bin -R --erase-user-data=secure

(but as normal flashers are missing -O flag support, you need to repartition with sfdisk)