Hi Tom,
unfortunately that plugin does not work. I have tried de-activating all plugs, deleting all custom css and also temporarily making posts public but the categories still do not show in alphabetical order.
Possibly they are showing in the order in which they were created.
I tested 2 other GP websites adding category widget to sidebars and they do show in alpha’ order.
if it’s not a GP thing I will try the WP forum
thanks