Editing output style has no effect on the document

Hi

I am attempting to change a citation from (Author and Author et al., 2001) to (Author et al., 2001) by going to Edit > Output Styles > Edit Output Styles > Citations > Author Lists > ‘If 4 or more authors list the first author etc…’

However, this is having no effect on any of my citations. Could anyone please help?

Thanks,

JM