Fresh Mask review for Facebook & Instagram

Setting up a FB shop was rather simple via this app, just click through and done. But I had a huge issue: in FB shop, 'checkout on the website' button on every product page would lead to an error page that reads 'Parameter Missing or Invalid: Required parameter missing or invalid: channel' I wrote to shopify support, got an answer that the issue was escalated to the technical team and I shall expect an answer in max 72 hours. Never heard back since. Very disappointed... Then I disconnect everything and re-install and re-create the shop, same error pages... Dont know what to do