I have problems to authorize my Testmachine. During Migration from 10.2.1 to 10.5.1 i installed my Developer machine and two Test machines with 10.5.1. On the 2nd Testmachine i wasn't able to authorize the machine anymore. Esri Support said that the Engine Developer Licence is a Single Use Licence. So may questions to ArcGIS Engine Developers. How do you authorize your Testmachine? I don't understand how to buy an Developer Subscription without being able to authorize test machines?