Tasks with actuals were changed to milestones in MSP, and then saved back to Clarity. The WBS page does not roll up actuals from milestones to summary tasks.
MSP supports actuals on milestones, but Clarity does not.
Open the project in MSP. For any task with actuals and the Milestone field set to Yes, change it to No. Save the project back to Clarity.
In Clarity, if a milestone had an assignment you cannot access the Milestone field, it is not active. The change needs to be made in MSP.