Pro Tools 11 session won't open on Pro Tools 8

Hi there



I work on Pro Tools 11 at home and on Pro Tools 8 at work.



I have a problem opening up sessions at work (on Pro Tools 8) that I saved at home on Pro Tools 11 as a Pro Tools 7-9 version.



Does anyone know why this is happening?



At home I save a copy in of my session as a Pro Tools 7-9 file, but at work it refuses to open up. Very frustrating!