Drawings completely disappear from one version of Harmony to the other

Hello, I’m working with a colleague on a project but he’s got a different version of harmony than I have ( he’s got Harmony 15 essential while I have Harmony 14 advanced )
I sent him a project we were working on, he colored it and sent it back to me, when I open it the frames were still the same but the cells were completely blank and all the drawings were disappeared .
This would sometimes happen when i used to work in Flash, some elements for example symbols would disapear when going from one version of the program to another, but it never happened to me to have all the drawings disappear, does anybody has ever had this kind of problem?
Please help me if you have any info on how to solve this
Thank you very much!

If you’re collaborating on a project together you should be using the same version
of Harmony. You can open a project created using an older version of the software
using the newer version but you can’t do the reverse.