Rescue data from iMac/MacBook that stuck on loading screen Disconnect the peripherals & restart your Mac Then, follow the proven solutions in this post to fix the MacBook Pro/Air or iMac that stuck on the loading screen with the progress bar: So, rescuing data from your Mac is a primary task. In fact, your Macbook won't turn on at all and froze on startup. But the sluggish progress bar still remains on the screen without any change. You may regard such a long boot process as a slow startup of your Mac and wait for hours. It usually happens after a recent macOS update, like a macOS Big Sur update, or macOS reinstallation.
That is your Mac stuck on the loading screen for a long time.
