I have now talked to 3 Microsoft support (2 from Powerapps tech support) & nobody was able to get my license to go from Trial to paid subscription.
Microsoft Rep #1 (PowerApps Technician)
I have in writing an internal Microsoft PowerApps technician telling me I can't have a paid subscription unless you are an E3, or E5. And they argued with me about it, after I said that Business Premium is supposed to be enough.
Microsoft Rep #2 (Office 365 rep)
After a Microsoft rep had me create an entirely separate license because your Microsoft.com docs lead them to a dead end. I had to explain how that could potentially lead to multiple instances with entirely separate environments, twice before they stopped insisting they didn't know if it would or wouldn't. They mentioned the internal interface is not matching your client facing one. And passed me over to PowerApps support again.
Microsoft Rep #3 (PowerApps Technician)
They showed me how making an app production is supposed to lead me to subscription activation. However had me add some capacity first, and told me to wait 24 hours for my new extra GB to show up. They said it is really strange that my paid PowerApps license is not showing up in the Office 365 Admin, and that I should call Office 365 support because something is not right. (Remember the only reason I have the license is because another rep told me to get it. But it's impossible to activate.)
Example: There is no upgrade, or payment link, or anything.
Microsoft Rep #4 (Office 365 Rep)
As per Rep #3(PowerApps Technician), I have to get them to undo what Rep #2 did.