Hi,

I found something interesting. Even I was unable to change the active field in my case. I debugged there is 1 query business rule that might be causing the issue so I used setWorkflow(false) before query and it updated the flag

update your code as below and try once:

var yearAgo = gs.daysAgo(365);

var gr = new GlideRecord("sys_template");
gr.addQuery('u_pre_approved', true);
gr.addQuery("u_approving_rfc.cab_date", "<", yearAgo);

gr.setWorkflow(false);

gr.query();

gs.print('** DEBUG ** ROWCOUNT :'+gr.getRowCount());

while(gr.next()) {
gs.print('** DEACTIVATING ** '+gr.name);
gr.active=false;
gr.update();
}

Mark Correct if this solves your issue and also mark Helpful if you find my response worthy based on the impact.
Thanks
Ankur