Ok I am throwing my weight in here because Planet's rooted android just does not work. It has the weirdest layout I have seen but the su binary (and yes it is an su binary) seems to have been linked to something different.
[blockquote]which su
/sbin/su[/blockquote]
[blockquote]ls -la /sbin
drwxr-xr-x 3 root root 300 2018-06-28 22:54 .
drwxr-xr-x 21 root root 0 2018-06-28 22:54 ..
drwxr-xr-x 5 root root 100 2018-06-28 22:54 .core
lrwxrwxrwx 1 root root 10 2018-06-28 22:54 adbd -> /root/adbd
lrwxrwxrwx 1 root root 23 2018-06-28 22:54 fuelgauged_static -> /root/fuelgauged_static
lrwxrwxrwx 1 root root 13 2018-06-28 22:54 healthd -> /root/healthd
lrwxrwxrwx 1 root root 15 2018-06-28 22:54 magisk -> /root/ltCXUKAph
lrwxrwxrwx 1 root root 15 2018-06-28 22:54 magiskhide -> /root/ltCXUKAph
lrwxrwxrwx 1 root root 15 2018-06-28 22:54 magiskpolicy -> /root/Hq3Bdj1rs
lrwxrwxrwx 1 root root 16 2018-06-28 22:54 multi_init -> /root/multi_init
lrwxrwxrwx 1 root root 15 2018-06-28 22:54 resetprop -> /root/ltCXUKAph
lrwxrwxrwx 1 root root 15 2018-06-28 22:54 su -> /root/ltCXUKAph
lrwxrwxrwx 1 root root 15 2018-06-28 22:54 supolicy -> /root/Hq3Bdj1rs
lrwxrwxrwx 1 root root 13 2018-06-28 22:54 ueventd -> /root/ueventd
lrwxrwxrwx 1 root root 15 2018-06-28 22:54 watchdogd -> /root/watchdogd[/blockquote]
[blockquote]cd /root
ls -la
drwxr-xr-x 2 root root 0 2018-06-28 22:54 .
drwxr-xr-x 21 root root 0 2018-06-28 22:54 ..
-rwxr-x--- 1 root root 790120 1970-01-01 01:00 Hq3Bdj1rs
-rwxr-x--- 2 root root 1095264 1970-01-01 01:00 adbd
-rwxr-x--- 2 root root 396600 1970-01-01 01:00 fuelgauged_static
-rwxr-x--- 2 root root 803616 1970-01-01 01:00 healthd
-rwxr-xr-x 1 root root 109600 2018-06-28 22:53 ltCXUKAph
-rwxr-x--- 2 root root 1262960 1970-01-01 01:00 multi_init
lrwxrwxrwx 2 root root 7 1970-01-01 01:00 ueventd -> ../init
lrwxrwxrwx 2 root root 7 1970-01-01 01:00 watchdogd -> ../init[/blockquote]
[blockquote]su
Permission denied
Planet:/ $ /root/ltCXUKAph
ltCXUKAph: applet not found[/blockquote]
Notice the timestamp on that binary. Seems it is just generated.
So on the off-chance I got a bum download I downloaded it again. Sadly though the md5sums match.
[blockquote]cb71a5aadaa2800221dba99f1d6cf055 root_boot.img[/blockquote]
So no point in re-flashing it as it will not solve the underlying issue. That of broken su binary.
EDIT: Ok so I got SU working again. I just installed Magisk Manager from the Git repo here
https://github.com/topjohnwu/MagiskManager/releases"\" target=\"_blank\"]
https://github.com/topjohnwu/MagiskManager/releases[/a]
0.5.7 installed and did not free this time. So dunno what I might have done to help that. But feed back from others say this is how they got SU to work properly as well.