security setting do not allow this mac to use external startup disk

Once you have erased the internal SSD of a T2 Mac, you have also erased all users & the ability to authorize any system changes. You would have had to modify those security settings prior to erasing the internal SSD.

Your only option now is to boot into Internet Recovery Mode to access the online macOS installer.

ronen179 wrote:

i have erase my disk

i want to install new os

when i start to do it from bootable disk with macos

it says " security setting do not allow this mac to use external startup disk"

when i do as follows in the instructions:

i have to restart and reopen with cmd +r pressed.

then i go to chage security

then it tells me needs to verify my self as system manager.

then tells me didnt find any manager

and i am in a circle and can not install any macos

please advice what i have to do

regards,

ronen

ref

About Startup Security Utility on a Mac with the Apple T2 ...