In some unique cases, daily database backups may fail which will lead to the file not being generated. When you SSH to view your database backups or view the files in the Cloud UI you may see a period when files are either missing or not available (note that daily database backups are only retained for the last 3 days).
You can try to debug this issue by using the ah-db-backup command in your command line when on the server. You can find reference to this command here: https://docs.acquia.com/cloud-platform/manage/ssh/drush/acquia-commands/#ah-db-backup
Sometimes, when manually running the command, the following error can be reproduced:
example@web-12345:~$ /usr/local/bin/drush -r /var/www/html/example/docroot ah-db-backup example Fatal error: Class 'Symfony\Component\Yaml\Yaml' not found in /mnt/www/html/example/docroot/sites/sites.php on line 61 Drush command terminated abnormally due to an unrecoverable error. [error] Error: Class 'Symfony\Component\Yaml\Yaml' not found in /mnt/www/html/example/docroot/sites/sites.php, line 61
In this specific case, there was a line in sites.php that referenced the following:
Removing this line will allow database backups to generate and you should see a successful message after running the ah-db-backup command once this code is removed.
If you are still having issue, please do not hesitate to reach out to Acquia Support.