If you need step by step directions then go the full unbrick route and copy your data off the user (ext4) partition first. Here is one such unbricking thread there are others:
https://community.wd.com/t/guide-how-to-unbrick-your-2tb-3tb-4tb-my-cloud/93336
You might not be able to simply push the rootfs.img file extracted from the latest firmware to the RAID partitions using the Linux command prompt command: sudo dd if=rootfs.img of=/dev/md0 or if the RAID is unmounted using the commands:
sudo dd if=rootfs.img of=/dev/sdb1
sudo dd if=rootfs.img of=/dev/sdb2
I posted a thread on the unbricking procedure I used (primarily to get around the no dashboard issue when upgrading from the v3.x firmware to the latest v4.x firmware). In the following post has the basic directions I’ve used several times now.
https://community.wd.com/t/unbrick-then-firmware-upgrade-equals-no-dashboard/136666/6
Later in that thread user Fox_exe posted a link to a method of possibly unbricking the My Cloud without removing the hard drive provided one can still access the My Cloud via TFTP. I haven’t tried it so no idea if or how it works.
https://community.wd.com/t/unbrick-then-firmware-upgrade-equals-no-dashboard/136666/19
If you don’t know how to issue Linux command line commands then do an internet search to learn how to open the Linux terminal window and how to issue commands in it.
