Does Nextcloud still work? Does the database exist?
/opt/rh/rh-mariadb105/root/bin/mysql --socket="/var/run/rh-mariadb105-mariadb/nextcloud-mysql.sock" -e "show databases;"
Did you already try to run the cronjob manually?
sudo -u apache scl enable rh-php73 -- php -d memory_limit=512M -d apc.enable_cli=1 -f /usr/share/nextcloud/cron.php
If this error just occurs once, it could be an issue that mariadb not started or restarting, see Problems with Nextcloud - #23 by dnutan