I have BF1-Origin and friends has BF1-Steam how can they join my platoon?

when I create a platoon my friends can see it when they are running their steam version, but they can't seem to join. nor do I get any notification that they are trying to apply nor do they see any way to apply.

is there something we need to do to have Steam players join my EA version platoon?? 

I have both an EA and Steam Account, but I don't think they are linked, read some post about linking my two accounts but no sure if that applies to this issue.

Tia.