The users with report_scheduler role are not able to see the types "excel" while scheduling a report.
When the user with report_scheduler rights is scheduling a report (table sysauto_report), only the following options can be selected in field "Type": PDF-landscape, PDF, PNG
When doing the same with admin rights, the field "Type" contains the following options: PDF-landscape, PDF, Excel (.xlsx), Excel (.xls), CSV.
Users with report_scheduler rights cannot modify the schedule and also the type will be changed from excel to pdf.
It happens in cases where the report is not shared with the user.
Check the scheduled report and corresponding report.
Check if the report is shared with the user.
If not, Please share the report with the user and try scheduling the report.
The user should be able to schedule the report with type as "Excel" and also all the below types should be available to the user
Please refer to the below documentation on reports administration.