only multiple citations are formatted when I "update citations", not single citations

In EndNote X3, I’ve just started using a new output style (American Journal of Industrial Medicine). However, when I “update citations”, single article citations do not format. Only when there are multiple citations together in the text do those get formatted. I’ve never seen this before in EndNote. I’ve gone into “edit output styles”, but none of the options seem to relate to this problem. Any ideas? Thanks.

Can you explain why you think only the single article citations aren’t formatted and that the multiple ones are?  What changes are you expecting to see that’s not happening?