Did the latest GOG galaxy update break the overlay in this game ? It was working with GOG Galaxy version 2.0.55 but it stopped working in 2.0.58 or 2.0.57 (not sure because I didn't test with 2.0.57). I also did a verify/update of the game files but nothing changed. Also I tried in DX11 and DX12 and no difference. Does the GOG overlay work for anybody ?
EDIT: Nevermind, I've just seen this. It's a known issue and will be fixed in the next update https://www.gog.com/forum/general_beta_gog_galaxy_2.0/2058_breaks_overlay_on_witcher_3/post3