This may be due to the particular delayed report being infrequently accessed. Check the lower right corner of the report to see when the last time the report was updated and compare that to other reports that are current:
The CloudHealth platform will pause processing of infrequently accessed reporting to ensure the highest level of performance possible. After 60 days, any reporting not accessed will become dormant and data will not be updated until that report is viewed in the future. Processing for dormant reporting will kick off immediately once an attempt to access it is made and fully updated data should be expected within 24-48 hours.
If you believe that certain reporting will be important to view on-demand without any delays, be sure to view that reporting within 60 day timeframe increments to prevent it from going dormant.