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dyn

macrumors 68030
Aug 8, 2009
2,708
388
.nl
The update will only install when you have the power adapter hooked up to your Mac. If you don't have it hooked up it will download and reboot your machine but when the firmware flasher wants to run it will bug out and reboot the machine back into OS X. If you do an update check in the MAS it will then once again tell you there is a Thunderbolt update. Have you tried to install it without the power adapter hooked up?
 
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