@botstub
Is this a corporate/company account you are using? If yes - ask your IT Support; they should know or direct you to whoever supports your Power Platform.
The default environment is generally open to all user accounts in the tenant; however, if it was set as manage the environment, you need a premium license to access it.
In the meantime, you can go to the web portal: https://make.powerautomate.com/
Then in the upper right corner, select environment and see if it does open. For example, in corp/work, you will most likely see a couple of settings depending on the company's strategy for managing the power platform and access.
You might have access to the environment but no access to register a new machine - it all depends on the operating model implemented.
