Metric Widget on Dashboard not pulling symbol anymore



I am hoping someone can help me to understand why I am getting an error now with my metric widgets in on a dashboard. Previously I was pulling a sheet summary into a metric widget that would show a "symbol" on the dashboard. Now it is showing an image error symbol and not pulling this through to the dashboard properly as it did before.

Anyone have thoughts to why this is not working any longer? Nothing was changed in the formulas or the way the sheets and dashboards were set up.