First of all, if it's a one time off, you shouldn't use a UI action for it. You should maybe create a scheduled script execution.
And you need to adapt your script a bit. Does this work for one record if you run it via background scripts?
var gr = new GlideRecord('ar_kb_knowledge');
gr.addQuery('kb_knowledge_base','dfc19531bf2021003f07e2c1ac0739ab');
gr.addQuery('dateGenerate','<','2017-01-01','12:00:00');
gr.addQuery('category','Planned Downtime');
gr.addOrCondition('category','Unplanned Downtime');
gr.setLimit(1);
gr.query();
while(gr.next()) {
gs.print('Archiving record with number: ' + gr.number);
try {
new GlideArchiveRecord().archive(gr);
}
catch(err) {
gs.log('Error returned is: ' + err);
}
}
