Big Sur fails to mount encrypted volume

I have a problem mounting an encrypted volume on Big Sur (11.1).
In DiskUtility, when I select the volume, click Mount, enter password and click Unlock, nothing happens.
I also tried to use CLI to unlock the volume using command:
Code Block 
diskutil apfs unlockVolume /dev/disk1s6

but it gives me error:

Passphrase:
ACM: LibCall_ACMContextCreate: returning, err = -536870181.
Error -536870181 (0xe00002db) creating ACM Context for passphrase

I also tried to create a new encrypted volume with simple password '123', but after I unmounted it and tried to mount again I got the same error.

Device: MacBook Pro (16-inch, 2019)

Is it a bug in Big Sur or am I doing something wrong? Should I just wait for an update with a fix?

I don't have an urgent need to decrypt the data because I have a backup. The question is about possibility of using encrypted volumes in macOS.
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Accepted Answer

I contacted support today with this issue and after few ideas they asked me, if I can access FileVault in preference and unlock it - I Was unable to do so - my password looked invalid.

Then they asked me to perform SMC reset and after that I was able to unlock FileVault and all my encrypted volumes mounted OK.

Now everything with encrypted APFS+ volumes works OK.
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Answers

Got the same issue with external drive on MacBook Pro (15-inch, 2019). Pretty sure got correct password for encrypted volume, but cannot mount it.

Any Ideas?
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qnox81
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I contacted support today with this issue and after few ideas they asked me, if I can access FileVault in preference and unlock it - I Was unable to do so - my password looked invalid.

Then they asked me to perform SMC reset and after that I was able to unlock FileVault and all my encrypted volumes mounted OK.

Now everything with encrypted APFS+ volumes works OK.
Posted by
qnox81
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I did these steps from the article and it works now. https://support.apple.com/en-us/HT201295

Before resetting the SMC, try these steps:
Shut down your Mac.
Press and hold the power button for 10 seconds, then release the button.
Wait a few seconds, then press the power button to turn on your Mac.


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