The participation rate for the job stress test is 30%. Can we close it as is?

Hello. We are conducting job stress tests for office workers and customer service personnel.
We have provided the test link to all employees and repeatedly notified non-participants, but the current participation rate is not rising beyond approximately 30%. Given the high likelihood that participants will not join even if the testing period is extended, we are considering whether to finalize the results as they are.
I am wondering if the results by department can be utilized even when many employees did not participate, and if I need to keep a record of additional notifications sent to non-participants.
What target participation rate do other companies aim for when conducting job stress tests? I would also like to know how you interpret results or manage follow-up for departments with low participation rates.