Testing my DKIM configuration and failed.

Hi,
As I was following this guide
I got stuck at the testing DKIM configuration step.
(My server is Debian10, I follow this guide because I saw others followed it and worked)

I run this command
PHP Code:sudo opendkim-testkey -d mydomain.com -s default -vvv
it shows

PHP Code:opendkim-testkey: using default configfile /etc/opendkim.conf
opendkim-testkey: checking key 'default._domainkey.mydomain.com'
opendkim-testkey: 'default._domainkey.mydomain.com' query failed

Here's the status of my OpenDKIM

PHP Code:opendkim.service - OpenDKIM DomainKeys Identified Mail (DKIM) Milter
Loaded: loaded (/lib/systemd/system/opendkim.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Thu 2021-02-04 04:36:35 CST; 38s ago
Docs: man:opendkim(8)
man:opendkim.conf(5)
man:opendkim-genkey(8)
man:opendkim-genzone(8)
man:opendkim-testadsp(8)
man:opendkim-testkey
http://www.opendkim.org/docs.html
Process: 4335 ExecStart=/usr/sbin/opendkim -x /etc/opendkim.conf (code=exited, status=78)

Feb 04 04:36:35 myhostname systemd[1]: opendkim.service: Control process exited, code=exited, status=78/CONFIG
Feb 04 04:36:35 myhostname systemd[1]: opendkim.service: Failed with result 'exit-code'.
Feb 04 04:36:35 myhostname systemd[1]: Failed to start OpenDKIM DomainKeys Identified Mail (DKIM) Milter.
Feb 04 04:36:35 myhostname systemd[1]: opendkim.service: Service RestartSec=100ms expired, scheduling restart.
Feb 04 04:36:35 myhostname systemd[1]: opendkim.service: Scheduled restart job, restart counter is at 5.
Feb 04 04:36:35 myhostname systemd[1]: Stopped OpenDKIM DomainKeys Identified Mail (DKIM) Milter.
Feb 04 04:36:35 myhostname systemd[1]: opendkim.service: Start request repeated too quickly.
Feb 04 04:36:35 myhostname systemd[1]: opendkim.service: Failed with result 'exit-code'.
Feb 04 04:36:35 myhostname systemd[1]: Failed to start OpenDKIM DomainKeys Identified Mail (DKIM) Milter.
Anyone on Debian10 have a solution for this?
THANKS A LOT!