Dashboard Subscription message "To view this component, open the dashboard in the full Salesforce site"

If the message is returned in the email, but not in the Salesforce user interface (UI), or if the message appears intermittently, it is likely that the component is timing out.This can often be resolved by improving the efficiency of the underlying report using the recommendations outlined in the additional resource article.

If there is an error in running the component, the error will likely be displayed when the dashboard is run in the full Salesforce UI. The error in the UI will be more descriptive and can be referenced to understand the issue. 

Subscription functionality can run one to two release behind, which means that when new functionality is released, the above message will be displayed for components utilizing the new functionality until it becomes compatible with Subscriptions. 
Impacted features include:
Row Level Formulas
Unique Counts
Field to Field Filtering