Can you attach a sample workbook? From what you said, it looks like you're aggregating on a aggregate which Tableau won't allow. You can use a level of detail function to bring down aggregate to fact and then apply another aggregate on top of it but we need to see how your data is structured.
Thank you for your reply.
As per your suggestion I attempted a LOD but it didn't work as the data is from two different sources. The sample book can be found on this link - I needed to use wetransfer as the file was too large to upload.
As stated in the original question, what I am trying to achieve is figuring out how many cases meet the SLA for each Sub Category both in % and in absolute terms.
Any potential suggestions/ solutions are welcome!
I can't get to workbook as our internet is blocking it. Can you create a small subset of data say with 100/1000 rows and upload it here?