* If the issue persists, reset NVRAM or PRAM. * If the issue persists, reset the SMC as described for notebook computers with a nonremovable battery.
* Unplug all external devices from your Mac, including any displays and USB accessories, and remove any card inserted in the SDXC card slot. As per the docuement, 'When you install macOS Big Sur on these Mac models, the installer might say that the update cannot be installed on this computer, or your Mac might start up to a blank screen or circle with a line through it.' In such cases, Apple has listed the steps below to resolve the issue: * Press and hold the power button on your Mac for at least 10 seconds, then release. Apple has released a support document where it gives steps to install macOS Big Sur on these MacBook Pro models. The affected Macbooks are said to be MacBook Pro (Retina, 13-inch, late 2013) and MacBook Pro (Retina, 13-inch, mid-2014). These users have claimed that their Macs show a black screen after they tried to install the new software. Several users of older MacBooks, particularly 20 models, have complained of their machines getting bricked after updating to macOS Big Sur.
