Live notifications aren't working

Preconditions:

• The Mail Sending should be configured
• An user exists and has an email address set in its profile
• Eventually, go to webapps\xwiki\WEB-INF\xwiki.properties and set notifications.emails.live.graceTime = 1 to enable the sending of e-mails after 1 minute. Make sure the line is not commented out (doesn't have an # at the start of it).

Steps to reproduce:

1. Log in as a simple user (with email address in the profile)
2. Click on the bell in the top right corner
3. Click on Settings, in the right side of Notifications
4. Set "Email Frequency" to Live
5. Set ON all the options in the Email column
6. Log in with another user or with Admin
7. Create/update/delete a page
8. Comment in another page
9. Mention the used user in the content of a page

Expected results: An email is sent to the user that has the notifications set to ON, Live.

Actual results: No email is received.

In the XWiki console the following message appears:

2020-08-17 15:57:04,272 [org.xwiki.notifications.notifiers.internal.email.live.MissingLiveNotificationMailsJob@70ab7969(null)] INFO  issingLiveNotificationMailsJob - Starting job of type [notificatiion.livemails.resume]
2020-08-17 15:57:04,292 [org.xwiki.notifications.notifiers.internal.email.live.MissingLiveNotificationMailsJob@70ab7969(null)] INFO  issingLiveNotificationMailsJob - Finished job of type [notificatiion.livemails.resume]

Note: The Live emails are working on 12.5.1