Ha! When I got my Synth - November last year - there was a card for a free pack, but when I looked there wasn’t anything ‘for Synth’ so I didn’t use it…
Of course now there are some Presets and a Scene back for the Synth I remember there’s a card for one…
…but the code is a discount for the cheaper earlier sample packs rather than Synth-specific ones 
I should join the newsletter.