Why I've already upgraded to pro account, and still have 40 minutes limit?

Hello,

I suspect that although you have paid for an upgraded account, you have not actually assigned the licence. Zoom does not do this part for you. You will need to act as the account admin and assign the upgraded licence to your account.

Assigning a single license

Sign in to the Zoom web portal.
Click User Management, then Users.
Locate or search for the user who you want to assign a license. (Your own account)
Click Edit at the end of the user row.
This will open a window.
Choose the User Type to assign.
After choosing the User Type, use the drop down to select the license.
Click Save.
The license is now applied and you can use it immediately.

https://support.zoom.us/hc/en-us/articles/16519456230285-Troubleshooting-paid-account-still-showing-as-basic 

Regards

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