FileVault Causes Startup Issues?

iMac (Retina 4K, 21.5-inch, Late 2015)
3.3 GHz Quad-Core Intel Core i7
16 GB 1867 MHz DDR3
Apple Wireless keyboard and mouse.
Big Sur latest. Booting from external T5.

I turned on FileVault on the external T5 (many hours to complete). When I rebooted the machine the keyboard and mouse were not connected so there was no way to choose a user or type a password. No ‘default’ user was selected and no password entry box appeared. I had to plug in the keyboard and use a USB dongle wireless mouse and hard reboot to get the machine up and running.

I turned off FileVault and (many hours later) the bootup problem resolved.

I’m assuming there’s some problem in the sequence of events that won’t check Bluetooth before a user/password is entered when FileVault is enabled, but I’m guessing someone here knows more about this.

Any ideas? If I install Monterey will the same problem persist? (I’d rather not spend the many hours turning FileVault on/off to experiment, but that’s my next step if no one here has any insight into the issue.)


I always used to have a wired keyboard and wired mouse available (normally connected to my secondary screen about 6 feet away from my iMac). In case there were Bluetooth issues on the iMac, I could plug one or both of them in to get going.

However, the current Mac Magic keyboards and pointer devices usually are recharged and paired by connecting them directly to the Mac via a Lightning to USB or USB-C cable. While connected that way, they use USB to pass commands, not Bluetooth. So, since I usually have a USB-to-Lightning cable attached to the iMac (since the Tracpad requires charging every few weeks), I connect that cable to the appropriate device for what I want to do until Bluetooth starts operating normally.

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