To learn a recipe, you need to get the idea for the recipe.
When the conditions for the recipe idea is met, a notification message will appear at the top of the screen, and a ◆ badge will be shown in "Recipes" on the home screen. Execute the command to get the recipe idea.
After getting the recipe idea, select the appropriate recipe and tap "Synthesize" to synthesize the item with the recipe.
If you still cannot learn the recipe after executing the "Recipes" command, you may not have met some of the conditions. Please tap that recipe in "Recipes" screen to see if there are any conditions in progress.