Unable to root Huawei Y6 SCL-L21

[Guest BananaPie]

Hello. First time poster here.

I have Huawei Y6 SCL-L21 model. First I rooted it as soon as I received it with KingRoot (I know, rookie mistake).

Then I had to factory reset it. There were some other complications, so I was forced to reflash stock ROM. I found the Swedish one that worked (not the original though).

After that, KingRoot didn't do it's job. So today I unlocked bootloader, flashed TWRP custom recovery, and flashed SuperSU zip on it.

It was supposed to be rooted, but when I entered SuperSU it told me that there is no SU binary installed and that SuperSU is unable to install it either.

Anyone else had this problem? 

I just want to root it back, but can't seem to find a way how to do it.

What did I miss?