Try to check all the users and extensions if the email is assigned anywhere in the account.

If the issue still exists, submit a support ticket to the developer support team. They can assist you in investigating the issue

I have done this already and can not see the email address used anywhere else i have logged a case but have not received a response back yet

Thank you

Any update, this is happening to me as well and I just start with RC ....

I just tested on my sandbox account. I deleted and re-add a new extension reusing the email address and it works well.

The best way is to create a support ticket so the developer support team can help take a look at your sandbox account.

If you had a Proof of Concept going in the past, with that email address entered - it is possible that only RC support can clear it out.

Not really. I login my sandbox as a normal user (an account owner) and delete/re-create and extension with the same email address.

Did you contact the dev support?

I too have run across an email already in use but can not find the account anywhere. Did anyone solve this?

Did you submit a support request?

This has happened to some folks in my company. Usually it's because they had tried to create their own Video Pro free account before IT has a chance to create it under the admin portal. Since there can only be one unique email address, once setup by the user, the IT admin cannot use it again. The solution is to have the user delete their account so that it's available once more. If they don't remember the password, select "forget password" to reset (assuming they can access the email).