Unable to schedule a Pivot/Multilevel Pivot report in excel format.
Pivot or Multilevel pivot reports can only be scheduled in PDF format. Screenshot below :
Unfortunately, we do not have the feasibility to schedule a pivot or multilevel pivot reports to excel.
This is working as designed and this functionality was never there in the OOB platform. If you need this functionality, it would be considered as an IDEA.
This would be a great candidate for an IDEA request to be implemented in future releases.
Please follow the KB article KB0755878 - Idea Management for customer enhancement requests while submitting an IDEA request. You can create an IDEA request with proper business justification and all the details about your request.
You can refer the Automate Report Distribution for more details