When Apple releases Mac firmware updates, the system undergoes a special installation procedure in which it shows a progress bar on a gray screen and then reboots. If you have an update available but do not see the progress bar when applying it, it may not have installed properly. As such, you may see the update still showing in Apple's Software Update service.
There are some special requirements for handling firmware updates as opposed to standard software updates, and if they are not met, the system may fail to install the update.
The first requirement is to ensure that … Read more