Are you saying you can get the file to play back in swing but that it exports straight?

If you can't get swing at all, see this...

https://makemusic.zendesk.com/hc/en-us/community/posts/214061088-Apply-swing-to-all-staves-in-the-middle-of-the-score 

and this to turn it off...

 https://makemusic.zendesk.com/hc/en-us/community/posts/219735568-Turn-off-swing-from-expression-selection-box 

All these and more were available by typing the term "swing" into the search box above.

Yes. The file plays back in swing, but exports straight