Starting with the release of Strategy ONE (March 2024), dossiers are also known as dashboards.
When a subscription fails during an underlying execution of a report, document, or dossier, there is no “Failed Subscription” error in the DSSErrors.log. Even if Failure Notifications have been configured, there is no Failure Notification sent to the email configured in Project Configuration.
The only errors seen in the DSSErrors.log are related to the execution of the job. For example, if you attempt to send a subscription to execution for Electronic Revenue vs. Forecast for a specific date:

In this scenario, there is a governing limit that will cause the report to fail during execution. As such, you would expect to see FAILED SUBSCRIPTION in the DSSErrors.log. However, only an error about the report failing to execute appears.
[SERVER:CastorServer][PID:188][THR:11356][Dimensional Storage][Error][0x80043E90][UID:54F3D26011D2896560009A8E67019608][SID:4F094B1ADBCE5F6C96CC89384703923F][OID:EB3CD5D14F4C8C77782AC0882C986B8D] Maximum number of results rows per report exceeded the current limit: 50. Please reduce the number of rows or contact the administrator to change the limit in the project configuration through Developer.
This is an identified defect in Strategy 2020.
This defect has been resolved in Strategy 2020 Update 1. Please upgrade to Strategy 2020 Update 1 or later to take advantage of the fix.