the32 bit version of Starfilter Pro 4 works my version 15.1 so I think it should work in 16 [but no guarantee]

the 64bit version does not work

that is probably because the 32 bit version is photoshop cs2 compatible which xara will recognise, and 64bit is photshop CC compatible which it may well not

that means when you set up the plugin in options/effects and plugins make sure you point to the starfilter folder in Program Files [x86] and not Program Files
EDIT - this assumes you have windows 10 - if you don't then it may well be different and you will need to let us know

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also make sure the box to enable host specific plugins is ticked as shown

this plugin only works on bitmaps [photos] not vectors, so make sure you don't have any vector in your selection

hope that helps

if you get error messages post them up as in Frances original post above:
tell us what the plugin was supposed to do and what happened when you tried to run it.