shopify register command keep getting "You do not have access to this feature"

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I tried to register an extension for app as learned on

shopify register --api_key=XXXXXXXX

It returns "You do not have access to this feature". 

I could not find any reference about this error. I have tried "shopify logout" and "shopify connect". Nothing seems to help.

Is this because the extension requires Shopify PLUS account? 

The extension was created from Argo checkout template

shopify create extension --type=CHECKOUT_POST_PURCHASE

 Thanks for any help!

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