I tried to install Catalina Security Update just now on my MacPro 2013, and after some time it started rebooting in an endless loop. After may be 10 reboots, I powered it off. Now it will not boot into anything. I tried Recovery Mode, Internet Recovery Mode, USB install media. It just will not boot and goes into a reboot loop - the Apple logo and progress bar appear; the progress advances a bit and stops; it reboots; Apple logo and progress bar appear again, the progress does not advance at all; it reboots again, and so on... in a loop.
I tried SMC and PRAM reset, same thing...
What are my options, and what could the problem be?
I tried SMC and PRAM reset, same thing...
What are my options, and what could the problem be?