Dovecot mail-crypt webmail can't read encrypted messages

[Serveria Support]

I'm trying to setup Dovecot with mail-crypt plugin with per-user 
encryption.

I have configured mail-crypt plugin as per official guide here: 
https://doc.dovecot.org/configuration_manual/mail_crypt_plugin/

After that I created a user and an encrypted key by running this 
command: doveadm -o \plugin/mail_crypt_private_password=12345 mailbox 
cryptokey generate -u mail at example.org -URf (replacing dummy data ofc)

I can log in to webmail (and Dovecot) just fine, emails are getting sent 
and delivered. I have also checked the storage and the messages seem to 
be stored encrypted.

However, I can't read the emails in webmail (just headers can be seen) 
and in Dovecot logs I can see the following error:

failed: Private key not available: Cannot decrypt key ### Cannot decrypt 
key ### <8632: Password not available (FETCH RFC822.HEADER)

There seems to be an issue with mySQL query. The query I'm using (Select 
username as "user", password,"%w" as userdb_mail_crypt_private_password 
from mailbox;) seems to work just fine, when run from mysql prompt it 
outputs the usernames and passwords, but the error is still there 
(Cannot decrypt key ### Password not available).

Any ideas? What am I missing?