SSRS not sorting correctly.
When you have issues and try modifying group properties and tablix sort property, and still the report doesn't take the sorting you select on the groups or the query. You just need to right click on the report name on the Solution Explorer window and select View Code.
This option will show you the xml version of the report where you can find the property SortExpressions
This entry will show up multiple times you just need to find the one that the report is using and change it to the field you need, save the xml version then close it to go back to the Designer mode.
I found the solution on the following blog which I recommend in case you're still having issues.
http://stackoverflow.com/questions/29515934/ssrs-not-sorting-correctly
Thanks.
