OK listen, it's VERY recommended to you to format your sysnand (your system if you are new to this
) because u want your sysnand to be as clean/fresh as possible because it might solve a very common problem in the downgrader that leads u to a softbrick, and if you will update through recovery mode to unsoftbrick, u will lost the option to downgrade for a very very long time!!!
BTW : downgrade ONLY through menuhax, because it is much more stable, and try to launch ftbrony (came with the HBL starter pack) and quit as fast as possible, and then go to PlaiSysUpdater.
Hope that I helped