Disable DomainKeys Identified Mail!

When I’m trying to enable dkim for some domains, I read that DKIM:

Removing DKIM records from DNS domain xxxxxxxxxxxxxx.net ..
.. already gone

Removing DKIM records from DNS domain xxxxxxxxxxx.org ..
.. already gone

Removing DKIM records from DNS domain xxxxxxxxxxxxx.com ..
.. already gone

Configuring mail server to stop using DKIM filter ..
.. done

Stopping DKIM filter ..
.. done

Disabling DKIM filter at boot time ..
.. done

Before this command, opendkim was running
After this command, opendkim will be stoped.

Some email send, for example to gmail, tell no DKIM.
After I restart opendkim, some email send, tell DKIM “‘FAIL’ with domain …”.
Then the options on “Email Setting → DomainKeys Identified Mail” are unchanged. No keys from dkim.

Any idea whats going wrong here?

I tried multiple time. Same results!

Operating system: Ubuntu Linux
OS version: 20.04.2
Webmin version: 1.973
Virtualmin version: 6.16
Usermin version: 1.823