Virtualmin won't enable DKIM

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

I am trying to get DKIM running on a server, but when I go to the System Settings->Email Settings->DomainKeys Identified Mail and select “Yes” for Signing of outgoing mail enabled? and save, rthe system seems to quite happily get everything going, but when I return to the Domain Keys page to get the key, Signing of outgoing mail enabled? is back to “No” and the domains have " DKIM is not current enabled" on their DomainKeys Options page.

No error messages anywhere.

syslog:

Apr 8 10:25:16 odysseymagazine systemd[1]: Starting OpenDKIM DomainKeys Identified Mail (DKIM) Milter…
Apr 8 10:25:16 odysseymagazine systemd[1]: Started OpenDKIM DomainKeys Identified Mail (DKIM) Milter.
Apr 8 10:25:16 odysseymagazine opendkim[10233]: OpenDKIM Filter v2.11.0 starting (args: -x /etc/opendkim.conf)

root@odysseymagazine:~# systemctl status opendkim.service
● opendkim.service - OpenDKIM DomainKeys Identified Mail (DKIM) Milter
Loaded: loaded (/lib/systemd/system/opendkim.service; disabled; vendor preset: enabled)
Active: active (running) since Thu 2021-04-08 10:25:16 UTC; 6min ago
Docs: man:opendkim(8)
man:opendkim.conf(5)
man:opendkim-genkey(8)
man:opendkim-genzone(8)
man:opendkim-testadsp(8)
man:opendkim-testkey
OpenDKIM
Process: 10224 ExecStart=/usr/sbin/opendkim -x /etc/opendkim.conf (code=exited, status=0/SUCCESS)
Main PID: 10233 (opendkim)
Tasks: 7 (limit: 7031)
Memory: 7.7M
CGroup: /system.slice/opendkim.service
└─10233 /usr/sbin/opendkim -x /etc/opendkim.conf

Does anyone have any ideas?

The server does not run Bind, DNS is on Cloudflare.

In Virtualmin go to the account you made the dkim keys for.
Under
Server Configuration->DomainKey Options
Does your key show? You should see —Private Key— ---Public Key— and the DKIM DNS records

If not? Does the account have permission to send mail?