Can't install macOS Monterey with FileVault enabled. Also can't disable FileVault.

[mukduk]

I've downloaded the update, but when proceeding with installation I am asked which disk to install on. When I select my only disk, I am told that "The volume can not be used because it is encrypted with a disk password."

I've never had issues with FileVault before when moving from Sierra through High Sierra, Mojave, Catalina, and Big Sur.

I considered temporarily disabling FileVault, and I can't seem to do that in System Preferences -> Security & Privacy -> FileVault -> Turn Off FileVault… but that button doesn't seem to do anything when clicked.

 

[macdos]

Note: "Some users are not able to unlock the disk."

I installed with filevault on, no problems.

 

[mukduk]

Note: "Some users are not able to unlock the disk."

I installed with filevault on, no problems.

I am the only user on this device, and I have been since I bought it in 2015. When I click that Enable users… button, similarly nothing happens.

 

[macdos]

I am the only user on this device, and I have been since I bought it in 2015. When I click that Enable users… button, similarly nothing happens.

Well, that is where the problem lies. You would need to add the root user for the installer to unlock the file.