The only thing that happened on the system was a minor upgrade of PHP8.1x that happened with apt.
In addition, I updated nextcloud using the web interface from 26.0.1 to 26.0.3. This happened without errors or issues.
In most of the posts, they say it is a DB issue, but the MariaDB is running, and also, some other websites I have that use the DB are running fine. Also, PhpMyAdmin is working fine.
I also restarted the system and SQL, and all is running fine.
Other than this, I do not really find anything I could be troubleshooting. My server is maintained using the WEBUZO admin. As I have a support contract with them, I also asked them to check the SQL installation, and they also insist that all is installed right. Also, it makes sense because the CRON was always working without issues.
Therefore, I am a bit stuck because the corn for NextCloud is quite important to ensure all is running as desired. Any ideas that I could try would be very welcome.
Thank you all for thinking about the issue and maybe giving some tips on what I could try to resolve this.