You said before you are already rooted. So another try of rooting would not do anything.
That thing with enabling Magisk to run on background was just my guessing. If it says installed, magisk should ask with popup window if you allow/dont allow root access for app that just requested it. So I was thinking maybe Magisk was killed by power management and cannot show you that popup.
Just from curiosity. When you connect that device to computer and run:
Does anything happen?
Normally su should hang and on display of the device magisk should ask for allowing root.
If you click allow, then you get root shell - you can check with whoami command. this is usualy enough for me for any operation.
"DEBLOATING" is possible without root access using command
Code:
adb shell pm uninstall -k --user 0 PACKAGENAME
It is good enough tool to even kill the device (factory reset with some keycombo usually helps) if not used with caution.