This error message can happen when a Data Collector is already running on your account or has not been stopped before you install/registering another Data Collector on another computer.

Adding a Data Collector slot
Multiple Data Collectors is perfectly fine to channel data to your account from different networks. There can only be one extra slot open at a time. Several empty DC slots can not be available at any given time ,the system is designed to only allow 1 open slot at a time.

As a dealer, you can go to the Admin > Data Collectors section, for the account in question, and press the "Add Extra DC" button to allow another Data Collector to connect to the account.

As a customer, contact your dealer to request adding another Data Collector to your account.