I suspect you used to have a P2 trial license that allowed you to see the Environments tab in the Admin Center (admin.powerapps.com). If the plan expired, then you don't have the ability to see that tab anymore.
I can confirm the above if you share the email you use to login to PowerApps with me in a private message. I can see if there is a way to unblock you, but I first have to check the status of your account and the licenses you used to have.
As discussed over PM, the best way to mitigate this is to either extend the trial if you already have one or start a new one that will give you access to the Environments tab in the Admin Center.
If that is not visible, even after you try the above, please do a complete logout/login (and ideal clear cookies). This will force a refresh of the plans and it should reflect in the portal and the Admin Center.