flutter in_app_pruchase - consumables Billing library version 4.0+ is required

I'm trying out the in_app_purchase, and everything works so far (even with test license and test buy), except consumables.

When I try to mark the IAP as consumable, then the developer console tells me the following:

"Billing library version 4.0+ is required to use this feature"

I've declared in pubspec.yaml dependencies

in_app_purchase: ^3.0.7

and also tested ^3.0.6

I've also set up android/src/main/AndroidManifest.xml with the following code snippets:

...
    <uses-permission android:name="com.android.vending.BILLING" />
...
        <meta-data
            android:name="com.google.android.play.billingclient.version"
            android:value="5.0.0" />
...

I'm only using internal testing track.

What might be the possible reasons?

1. Is it an merchant account problem?
2. Might it be a play console problem?
3. Did I forgot something in my project?

Thank you in advance for your help

from flutter in_app_pruchase - consumables Billing library version 4.0+ is required