Same here! This morning everything was fine, now I can't pass SN check and therefore I can't play Pokemon Go :S
EDIT: I've tested everything, uninstalling magisk does nothing, even going back to the stock kernel does nothing: if the "System Status" flag is in "Custom" (instead of "Official") SN fails. Once you flash TWRP => the flag is set to custom and SN fails. Seems like for now I'll not be able to use SHealth as without root or a custom recovery I can't edit the build.prop. Thanks google!