Hi @PowFlexiXiong,
@yashag2255 is correct, HTTP conector is Premium.
Just do add some additional information:
Currently, Office 365 licenses give you what is called Seeded PowerApps, which is limited Power Apps capabilities, which are included in various Office 365 and Dynamics 365 licenses.
The features these licenses give are displayed in the image bellow:

For additional information, please access our Licensing Guide.
Nevertheless, do bear in mind that the licensing model has received a new change recently, and it is no longer used with P1 and P2 licenses plans.
The new licensing plans that are currently available are:
Power Apps
New and renewing customers will have the flexibility to choose PowerApps per app or per user plans.
- PowerApps per app plan. Allow individual users to run applications for a specific business scenario based on the full capabilities of PowerApps. Pricing will be $10 user/app/month.
- PowerApps per user plan. Equip individual users to run an unlimited number of apps, without any feature restrictions. This takes the place of existing P1 and P2 plans and will be $40 /user / month.
A brief description of the plans is also available in the Licensing Guide as seen in the image bellow:

I hope this info helped you get a better understanding on our Licensing model!
Regards,
Ricardo