Installation error: upgrade from Sierra to High Sierra
I have Mac Mini, late 2012. I want to upgrade OS from Sierra to High Sierra. Everything goes fine, just it all stops right before the first restart. Error message is installation error ("An error ocured while preparing the installation. Try running this application again."). I tried a couple of times but the error message appears always at the same moment and suspends the upgrade.
I upgraded to Sierra recently without any problems. Swithed off and on my Mac a couple of times. I also disconned the comp from electricity for a while. I also tried to upgrade directly to Mojave, but there is identical problem.
Thanks for help.