Hi, since the April 2018 release, it is not possible to sort A-Z on a chart axis, only Z-A. When clicking A-Z on the dropdown elipses, nothing happens. It is possible to sort by a measure but not A...
Same issue here and joining my post:
http://community.powerbi.com/t5/Service/Sort-A-to-Z-impossible/m-p/408308/highlight/false#M44060