If you have it already researched, try running:
/c game.player.force.reset_recipes()
It should refresh all the recipes.
Since you're the second to suggest a forum thread, I'll probably just make it ;)
Cheers TRK
EDIT: Ok, sorry - just tested the command and it doesn't do what I expected.
/c game.player.force.recipes["crafting-combinator"].enabled = true
This should work then