Really sorry to know about it. Can you let us know the previous version you were using ? I think it must have been below 4.0.
Regarding the API, i think you have used a Free Test API key last time. It was for one font conversion which has been already used. Currently we have disabled the free test key due to spamming. It was making our server down repeatedly.
For unlimited key payment is required. You can slide the slider to change the amount you want and get the premium key. That key comes with unlimited activation and unlimited font conversion.