Exporting a Multi-Level Pivot table type report to PDF failed

Exporting a Multi-Level Pivot table type report to PDF results in error: Export failed.
An unexpected error has occurred. Please see the instance logs for more details.

1. Create a Multilevel pivot report:
   https://docs.servicenow.com/csh?topicname=create-multilevel-pivot-report-rd.html&version=latest#create-multilevel-pivot-report-rd
   
   2. Data Values:
   Report name: test
   Source type: Table
   Table: Incident
   
   3. Type:
   Select Multi-level pivot table (under Multidimensional reports)
   
   4. Configure:
   Select columns: Additional Comments
   Select rows: Number, Assigned To, Short description
   Aggregation:
   Sum
   Duration
   
   5. Click Save
   
   6. Click Share and from the Sharing menu, click Export the Report to PDF, Generate now and Click Export.
   
   Expected behavior: The report should be exported to PDF.
   
   Actual behavior: You will get an error:
   
   
   
   The instance logs show below:
   
   2018-12-20 15:40:42 (744) glide.background.generation.e2978f3cdbeae7007826ffb41d9619a2 SYSTEM txid=2a97cf3cdbea SEVERE *** ERROR *** com.snc.whtp: An error occured on the server
   2018-12-20 15:40:42 (751) glide.background.generation.e2978f3cdbeae7007826ffb41d9619a2 SYSTEM txid=2a97cf3cdbea SEVERE *** ERROR *** Loading pages (1/6)
   [> ] 0%
   [======> ] 10%
   [==============================> ] 50%
   [============================================================] 100%
   Counting pages (2/6)
   [============================================================] Object 1 of 1
   Resolving links (4/6)
   [============================================================] Object 1 of 1
   Loading headers and footers (5/6)
   Printing pages (6/6)
   [> ] Preparing
   [============================================================] Page 1 of 1
   Done
   Exit with code 1 due to network error: AuthenticationRequiredError

1. Go to the report.
2. Click the Settings button (with the gear icon) on the right side of the banner frame.
3. In the General tab, click the icon of the printer to the right of Printer friendly version.
4. Use the browser's print functionality to save the report as PDF.