Handle edge cases in notifications

**Problem**
When working with services, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

No file, test, or notification entry point is identified in the issue. First locate the services and notification error-handling paths, then inspect existing tests and reproduce the relevant edge cases; done means the affected failures have descriptive messages and regression coverage.

Written by the indexing model from the issue text.