I believe there is a bug in Pivot Tables when both a conditional formatting and a filter action are defined. After the filter has been used and disabled again (by clicking at the filtered row again), the cells for whom a conditional formatting is applicable stay “grayed out”. The issue can be reproduced as shown below.
Create a PivotTable and specify a conditional formatting rule for the text color.
In my example I set the text color to red if the sum of values is less than 100,000.
Create a filter action
Apply the filter by clicking a cell
Click the cell again to disable the filter → the cells with the conditional formatting (which should have the red text color in my example) stay disabled and are thus hardly readable.
This has been reported by other community members as well. I recreated this in my environment and got the same issue. At the moment, the only substitute I was able to find is if you use a Table visual instead of a Pivot Table, but if this is not an option, I would highly recommend opening a support ticket: Case management - AWS Support.
Here are the other community posts where users raised the same behavior: