Dashboards: "Unable to display widget"

We have had a widget on our dashboard to display our company calendar for the last 6+ months and all of the sudden last week it stopped working and just displays "Unable to display widget". I haven't made any changes to the table or report.

Has anyone experienced this bug or found a solution to this in the past?

I have already tried changing every setting I can think of within the report itself, the dashboards, deleted the widget and added it back, and cant find anything that works.

Thanks for the help!