Power BI allows you to upload an Excel file that contains a report that gets data from the PowerPivot data model. When you refresh the report on the Power BI report gallery, you may get an error after 30 seconds
An error occurred while working on the Data Model in the workbook. Please try again.
The 30-second timeout starts when you start running the report. Behind the scene, when MDX queries are executed on the PowerPivot data model, there is a timeout on each MDX query. The first query has a 30-second time. If the first query takes 2 seconds to finish, the second query has a 28-second timeout. If the second query takes 3 seconds to finish, the third query has a 25-second timeout. When the 30-second total timeout is past since the report refresh starts, the error above is thrown.
The best practice to avoid this problem is to reduce the PivotTables/PivotChart each slicer is connected to. Try reduce the complexity of the PivotTable/PivotChart report and the PowerPivot data model. If the report takes 30 seconds to refresh on an Excel client, then it is likely going to take longer than 30 seconds to refresh on the Power BI. In my testing, I found Excel client report runs faster compare to Power BI web site report execution. My machine is an Intel Core i7 2.9GHz machine.
This 30-second timeout does not apply to Power BI Excel file scheduled refresh.