It is now working on GOG galaxy launcher :

"go to Panzer Corps 2 in your Library in GOG Galaxy, select the Settings button (the two sliders next to Play), then Manage Installation and then Configure. The DLC's should show both Panzer Corps 2 DLC 1 and Panzer Corps 2 Bonus Scenarios."

--> then ...

is it normal that with GOG version, there is not yet the DLC ? I have the field marshal edition and always the message " first two DLC (coming soon) " in the GOG launcher and when i click on it for download : " problem of server"

I try to launch PC2 with juste the slitherine launcher and no ...