We don't receive gems for each level of recipe mastery, just for level 2 and 4 - you can find the details for each level of mastery here in the BS Game Guide.
If you're not receiving the gem reward right away for those specific levels, first step would be to force close your app and reopen it which sometimes helps rewards show. If that's not the case and you're just not receiving the rewards at all, you will need to Open a Support Ticket with the team. Hope this helps!