I understand your problem as i ran into it myself but this was caused by yourself or myself in my case. There is a staging service for testing which you can use for testing things out which is called with the additional param --test-cert. The staging service has higher rate limit and is there for exactly that reason.
Use staging until you have your setup working and then request one from production - should by fine be now.
[quote]
We recently (April 2017) introduced a Failed Validation limit of 5 failures per account, per hostname, per hour. This limit will be higher on staging so you can use staging to debug connectivity problems.[/quote]