Hi tmiask12,
The scenario you are describing sounds like you are seeing a blank Output Viewer window and blank Data Editor window. Is there also a splash screen indicating that your IBM SPSS Statistics 26.0 product is not licensed?
It has happened for some users in the past where a working version of SPSS Statistics needs to be re-licensed after upgrading the macOS underneath it. To re-license your product, run the "SPSS Statistics License Authorization Wizard.app" you'll find just above the "SPSSStatistics.app" in your "Applications ->IBM->SPSS->Statistics->26" menu path.
If re-licensing the product fails to work for you, please go to the IBM Support site and open a Support case so they can help you troubleshoot the problem.
SPSS Statistics Support URL: https://www.ibm.com/mysupport/s/topic/0TO500000001yjtGAA/spss-statistics?language=en_US
Open a Support case using the "Open a Case" button in the upper right of the web page.
You might also review this blog item discussing IBM SPSS Statistics and macOS Catalina:
https://developer.ibm.com/predictiveanalytics/2019/10/08/spss-statistics-on-catalina-macos-10-15/
I hope this helps!