How to change encryption type (user key to master key)

help

#1

my owncloud server env is:
centos7.5
ownCloud 10.0.10
php7.2
Apache/2.4.6
MariaDB-5.5.60

I used this order:
occ app:enable encryption
occ encryption:enable
occ encryption:select-encryption-type masterkey
but,zhe prompt is : User keys already enabled
So ,how can I change the user key to master key?
who can help me?