I am going to copy this reference and summary. Please let me know if this helps. Thank you!
*In ANSYS Mechanical, if you are unable to view the participation factor in pre-stress modal analysis, it could be due to the use of the PCG solver with Future Analyses set to None. In this case, the .full file is not written, and mode participation factors are not extracted ("Title: In a Modal Analysis of Mechanical, why aren't the Participation Factors Summary under Solution Information displayed?", ANSYS Knowledge Resource).
To resolve this issue, you can change the Solver Type to Direct or set Future Analysis to MSUP Analyses. This should bring back the worksheet summary with the participation factors.