"Thanks for your reply."
Translation:Merci pour ta réponse.
I put that and I don't know why it is wrong - all the info on the net points to it being correct. Hopefully someone can let us know for sure
I think both are correct. I certainly can find multiple examples of both online. I'd report it.
Could it be that Merci de (before it's done). Merci pour (after whatever we are thanking for has been done/given to us?
I think "réplique" has something of an argumentative meaning. More like a "comeback" or a "retort" than a "reply".